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P01
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EPOSTER - 01 Acoustics
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17883 - Combined approach for large vestibular schwannomas: long-term follow-up in a series of 46 consecutive cases.
Combined approach for large vestibular schwannomas: long-term follow-up in a series of 46 consecutive cases.

Background: Microsurgical management of large vestibular schwannomas (VS) yields a high risk for the facial and cochlear nerve functions. Gamma Knife radiosurgery (GKRS) allows optimal functional results in small- and medium-size VS, but cannot be used upfront in large VS because of the high rate of volume-related side effects. 

Methods: In this context, we developed a new treatment paradigm of combined approach with planned subtotal microsurgical excision and GKRS, aiming at optimal functional outcome for the facial and cochlear nerves in patients with large VS (i.e. Koos grade IV). We report our long-term follow-up using this approach. 

Results: A consecutive a series of 46 patients was treated between 2010 and October 2018. The mean presurgical tumor volume was 11.3 cm3(1.47-34.9). The mean follow-up after surgery was 36.9 months (range 6-96). All cases had normal facial nerve function (HB I) before surgery, except for one who was in HB IV. Postoperative status showed normal facial nerve function (House-Brackmann grade I) in all patients. In a subgroup of 26 patients in which cochlear nerve preservation was attempted at surgery (patients with residual hearing before surgery), 24 of them (92.3%) retained residual hearing. Among them, 17 patients had normal hearing (Gardner-Robertson class 1) before surgery, and 14 (82.3%) retained normal hearing after surgery. The mean duration between surgery and GKRS was 6.2 months (4-13.9, median 6 months). The mean tumor volume at the time of GKRS was 3.2 cm3(0.5-9.9), which corresponds to a mean residual volume of 31.7% (range 3.6-50.2) of the pre-operative volume. There was a tendency towards larger postoperative residual volume in patients with attempt to cochlear nerve preservation. The mean marginal prescription dose for GKS was 11.9 Gy (median 12 Gy). Four patients were considered a failure and benefitted from a second combined approach in 3 cases and GKRS only, in one case. Three patients had a shunt. 

Conclusion: The current data suggests that the combined management of large VS with planned subtotal resection followed by GKRS may yield an excellent clinical outcome with respect to retaining facial and cochlear nerve functions. Our results with this approach are comparable to those obtained with upfront GKRS alone in small- and medium-size VS. 

 

Marc LEVIVIER (Lausanne, SWITZERLAND), Constantin TULEASCA, Michaela DEDECIUSOVA, Mercy GEORGE, Luis SCHIAPPACASSE, David PATIN, Raphael MAIRE, Roy Thomas DANIEL
09:00 - 18:00 #17839 - Fate of cystic enlargement of vestibular schwannoma after gamma knife radiosurgery : insight into pseudoprogression based on 2 cases reports with long-term follow-up.
Fate of cystic enlargement of vestibular schwannoma after gamma knife radiosurgery : insight into pseudoprogression based on 2 cases reports with long-term follow-up.

Background: Gamma kniferadiosurgery (GKRS) has been accepted as a safe and effective treatment in patients harboring a vestibular schwannoma (VS). However, during follow-up, tumor expansion induced by irradiation can occur and diagnosis of failure in radiosurgery of VS is still controversial. Tumor expansion with cystic enlargement causes some confusion regarding whether further treatment should be performed.

Materials and Methods: We investigate the change of cystic enlargement in VS after GKRS during the long-term follow-up period and propose the possibility of pseudoprogression to prevent unnecessary and inappropriate surgery.

Results: A 57-year-old male with hearing loss was treated with GKRS (12Gy, isodose 50%) for the left VS and thepreoperative tumor size was 0.8cc.This tumor started to increasein size with cystic change from the third year after radiosurgery and increased to 10.8cc at 5 years after radiosurgery.At 7 years after GKRS, the size of the tumor began to decrease on follow-up, and the volume of tumor was degenerated to 1cc in the 11 years follow-up.A 66-year-old female with dizziness and gait disturbance was treated with GKRS for the left VS (13Gy, isodose 50%). Thepreoperative tumor size was 6.3cc and the tumors started to increase in size with cystic enlargement from the first year after radiosurgery and increased to 18cc at 5 years after radiosurgery. The tumor maintained a cystic pattern with a slight change in size but no other neurologic symptomsduring the follow-up period.The regression of tumor was observed at 11 years after GKRS and the volume of tumor was decreasedto 3.2 cc in the 13 years follow-up.In both cases,continuous enlargement of the tumor cyst had observed over 5 yearsafter GKRS, and then tumor became stable afterwards. Over 10 years after GKRS, the cystic portion of the tumor has declined significantly.

Conclusions: Enlargement with cystic formation in the first3 to 5 years after GKRS has been considered as treatment failure.Based on our cases, however, additional treatment for cystic enlargement of VSshould be delayed until at least 10 years, especially in patient without neurological deterioration.

Shin JUNG (Jeollanam-do, KOREA), Gwang-Jun LEE, Kyung-Sub MOON, Woo-Youl JANG, In-Young KIM, Tae-Young JUNG, Sa-Hoe LIM
09:00 - 18:00 #17793 - Fractionated stereotactic radiation therapy for large vestibular schwanomas.
Fractionated stereotactic radiation therapy for large vestibular schwanomas.

Background : Managements for vestibular schwanoma include observation, radiation and microsurgical resection. If the tumor shows signs of growth, or causes neurological deterioration, treatmqent with microsurgery or radiation therapy is considered. Stereotactic radiosurgery have established effective treatment for small- to medium-sized vestibular schwannomas. In large tumors with radiological or neurological signs of brainstem compression, microsurgery is applied because radiosurgery cannot be used safely due to the high risk for radiation-induced complications associated with large volume of the tumors. However radical surgery might yields unacceptable complication. Our institute applies fractionated stereotactic radiation therapy (FSRT) for the treatment of vestibular schwanomas when the volume of them are large. In this study we evaluated the efficacy and the role of FSRT considering control of large vestibular schwanomas.
Materials and Methods : Between July 2006 and December 2018, we treated 7 patients with large vestibular schwanomas by FSRT using Novalis. The mean age of the patients at FSRT was 45.7 (range, 29 to 61) years. The mean planning target volume of all tumor was 26.6 (range, 12.8 to 46.2) ml and the mean prescription dose at the tumor margin was 40.4 Gy (range, 35 to 42.5 Gy / 10-17 fraction) .
Results : The median follow-up time was 40.3 months (range 9 to 86 months). All patients were alive at the last follow-up visit without receiving additional surgery or irradiation. Four patients out of 7 presented tumor shrinkage and the other 3 patients showed no change in size. No patients demonstrated neurological deterioration compared with the condition at FSRT. 
Conclusion : FSRT is thought to be an effective management option for patients with large vestibular schwanomas.

Takahiko TSUGAWA (Nagoya, JAPAN), Chisa HASHIZUME, Sachko KATO, Yoshimasa MORI
09:00 - 18:00 #16943 - Gamma Knife radiosurgery as first intention treatment for intravestibular and intracochlear schwannomas.
Gamma Knife radiosurgery as first intention treatment for intravestibular and intracochlear schwannomas.

Background

Schwannomas of the VIII-th cranial nerve are benign tumours, with vast majority occurring in vestibular division. Rarely, can also arise from distal branches of cochlear, superior or inferior vestibular. We review our experience with Gamma Knife radiosurgery (GKR), as first intention treatment for intracochlear (ICS) and intravestibular (IVS) schwannomas.

Methods

A total number of 5 patients were analysed, treated over 8 years, between June 2010 and September 2018, with Leksell Gamma Knife Perfexion or Icon (Elekta Instruments, AB, Sweden). The marginal dose prescribed was 12 Gy at a mean prescription isodose line of 61.4% (range 50-70). Clinical evaluation included auditory and facial function. 

Results

The mean age was 49.9 (range 34-63). The mean follow-up period was 52.8 months (range 12-84). The mean target volume (TV) was 0.087 ml (range 0.014-0.281). The mean maximal dose received by the cochlea was 11.2 Gy (range 2.6-20.3). The mean marginal dose received by the vestibule (e.g. utricula) was 14.2 Gy (range 3.8-17.5). No patient experienced an acute or subacute clinical adverse radiation effect after GKR. Four cases had overall symptom stability. In one patient (1/5), the vertigo, which was the main clinical complain, disappeared one year after GKR. However, it reappeared 3 years latter, with same pretherapeutic characteristics and is currently fluctuating. One patient experienced hearing decrease after GKR, during the first 12 months. This case received 11.2 Gy to the cochlea. Follow-up MRI course showed a decrease in size in four patients, and stability in one.

Conclusions

Gamma Knife radiosurgery is a valuable first intention treatment for ICS or IVS, in selected cases. Special attention should be paid for the dose delivered to the cochlea and the vestibular apparatus. Acute and subacute clinical effects are exceptional, while tumour control was achieved in all cases in our small series. 

Constantin TULEASCA (Lausanne, SWITZERLAND), Mercy GEORGE, Luis SCHIAPPACASSE, David PATIN, Raphael MAIRE, Marc LEVIVIER
09:00 - 18:00 #17680 - Gamma knife radiosurgery for large vestibular schwannoma more than 10cc: An Indian outlook.
Gamma knife radiosurgery for large vestibular schwannoma more than 10cc: An Indian outlook.

OBJECTIVE :

Stereotactic radiosurgery (SRS) is an important alternative management option for patients with small- and medium-sized vestibular schwannomas (VSs). Its use in the treatment of large tumors, however, is still being debated. We reviewed our recent experience to assess the potential role of SRS in larger-sized VSs who refused surgery or had co-morbidity.

METHODS Between 2006 and 2016, 34 patients with large VSs, defined as having a volume > 10 cm3, underwent Gamma Knife radiosurgery (GKRS) were analyzed. Clinical, radiological and radiosurgical parameters were studied. Post op tumor control, patients requiring surgery, factors predicting tumor failure were analysed.

RESULTS The median follow-up duration was 36 months (range 12-72 months). 7 patients (29.7) had previously undergone resection. The median total volume covered in this group of patients was 10.8 cm3 (range 10.0-13.5 cm3). The median tumor margin dose was 11.75 Gy (range 11-12 Gy). Mean size of tumor was 3.0cm (2.8-3.5)

All 34 patients had regular MRI follow-up examinations. Five had a volume reduction of greater than 50%, 12 had a volume reduction of 15%-50%, 14 were stable in size (volume change < 15%), and 3  had larger volumes. All patients had severe to profund hearing loss. Five patients has new onset deficits.  Four patients (11.76%) underwent surgery due to various reasons in one year duration after GKRS. Tumor control was achieved in 30 patients (88.24%).Patients having multiple cranial nerve involvement with cerebellar signs are the factor which predicts GKRS failure (p<0.0001). All other factors like age, sex, marginal dose, single cranial nerve involvement are not significant


CONCLUSIONS Although microsurgical resection remains the primary management choice in patients with VSs, most VSs that are defined as having both a single dimension > 3 cm and a volume > 10 cm3 and tolerable mass effect can be managed satisfactorily with GKRS.

 

Prabu Raj ANDIPERUMAL RAJ (BANGALORE, INDIA, INDIA), Arivazhagan ARIMA, Dhananjaya BHAT, Dwarakanath SRINIVAS, Sampath SOMANNA
09:00 - 18:00 #17731 - Long term (>10 year) outcomes of gamma knife radiosurgery for vestibular schwannomas: Single Center Study.
Long term (>10 year) outcomes of gamma knife radiosurgery for vestibular schwannomas: Single Center Study.

Introduction: Gamma knife (RS) has now been accepted as a treatment option for Vestibular Schwannoma (VS), either in combination with surgery or alone since last past two decades. The ultimate aim has therefore been to achieve maximum tumor control along with preserved neurological functioning. There have been only few reports evaluating the long term treatment outcome of RS for VS; all but two limited to 5 years follow up.

Objective: To present the 10 years follow up data on patients treated with RS for VS. Also we wanted to assess the factors responsible for failure of RS and worsening neurology.

Results: A total of 77 patients treated with Gamma Knife from the year 1997 to 2007 and available for follow up were ambispectively reviewed. Majority of them were treated with primary GK (73%) and most of them were Koo’s grade 3 (12%) and 4 (56%). Ten-year tumour control rates with Gamma Knife radiosurgery (RS) were at 81-100%. The tumour marginal dose was 12 Gy and revealed 10-year tumour control rates of 89%, hearing preservation rates of 50%, facial nerve preservation rates of 96% and trigeminal preservation rates of 93%. The tumor control rate was affected by the nature of the tumor , solid vs cystic. The neurology of patient’s post RS largely depended on the Koos grading of the tumor. No secondary malignancy or long term radiation adverse effects were observed in these patients.

Conclusion: RS remains a viable option for treatment of VS, with a good tumor control rate even on long term follow up. It may be used as a primary modality of treatment for small to medium sized lesions. However, for larger Koos grade tumor, a careful patient selection is required because of the chances of worsening cranial nerve functioning.

Ambuj KUMAR, Rajinder THAYLLING (New Delhi, INDIA), Shweta KEDIA, Hardik SARDANA, Deepak AGARWAL, Manmohan SINGH
09:00 - 18:00 #17700 - Radiosurgery for facial nerve schwannomas: a case report.
Radiosurgery for facial nerve schwannomas: a case report.

Background: Facial nerve schwannomas are benign, rare tumors which constitute less than 2% of intracranial schwannomas and less than 1% of intrapetrous mass lesions. Due to the very low incidence of this condition and its occurrence anywhere along the facial nerve tract, its treatment is controversial.

Objective: To describe the case report of one patient with facial nerve schwannoma treated with radiosurgery and to evaluate the follow-up of tumor control and functional evolution.

Materials and Methods: A 55-year-old female patient with facial palsy and vertigo was referred to the Radiosurgery Department at the Hospital Español, Mexico City. The patient was examined with CT and MRI scans, audiometry, logoaudiometry and electroneuronography of the facial nerve. Once the diagnosis of facial schwannoma was confirmed the patient was treated with cone-based radiosurgery using a Novalis 600N 6 MV (BrainLab) linear accelerator using 7 circular arcs. A total dose of 13.2 Gy was delivered to 100% of the tumor volume of 0.032cc; the dose to the cochlea and vestibule was 6 Gy. The patient has received to date a three years and six months follow-up.

Results: The tumor was located in the right mastoid tympanic junction (intrapetrous, second knee of the facial nerve) with MRI. Initially the patient was classified as grade V in the House-Brackmann scale; two years after treatment the patient showed a minor improvement and was classified as grade IV. The audiometry and logoaudiometry report have been normal to date but the patient has an abnormal right facial electroneuronography. Tumor control is 100%. After the radiosurgery the patient received rehabilitation therapies.

Conclusions: Radiosurgery is a safe technique for the treatment of facial nerve schwannomas, sparing the organs at risk and preserving organ functions. Radiosurgery is a good alternative for the treatment of small and medium-sized facial schwannomas.

Claudia Katiuska GONZÁLEZ-VALDEZ (Mexico City, MEXICO), Lourdes Olivia VALES HIDALGO , César DÍAZ-PÉREZ , Ana CANO-AGUILAR, Javier Emiliano SÁNCHEZ GUERRERO , Eric HERNÁNDEZ-FERREIRA, Raúl FLORENTINO GONZÁLEZ, Rebeca GIL-GARCÍA
09:00 - 18:00 #17558 - Stereotactic radiosurgery is associated with significantly decreased hearing preservation for vestibular schwannomas versus fractionated stereotactic radiotherapy.
Stereotactic radiosurgery is associated with significantly decreased hearing preservation for vestibular schwannomas versus fractionated stereotactic radiotherapy.

Isaac Yang, MD1-7 , Methma Udawatta, BS1,7, Isabelle Kwan1, Komal Preet, BS1,7, Thien Nguyen, BS1,7, Vera Ong1, John P. Sheppard, MS1,7, Courtney Duong, BS1, Prasanth Romiyo, BS1, Percy Lee, MD2, Stephen Tenn, PhD2, Tania Kaprealian, MD1,2,4, Quinton Gopen, MD3

 

Departments of 1Neurosurgery, 2Radiation Oncology, 3Head and Neck Surgery, 4Jonsson Comprehensive Cancer Center, 5Los Angeles Biomedical Research Institute, 6Harbor-UCLA Medical Center, 7David Geffen School of Medicine of the University of California, Los Angeles (UCLA), Los Angeles, CA, United States

 

ABSTRACT

Background: Vestibular schwannomas (VS) are benign intracranial neoplasms arising from the eighth cranial nerve for which targeted radiation therapy (RT) has proved increasingly successful. Long-term hearing and related cranial nerve outcomes, however, have been disputed for the three current RT modalities.

Objective: To determine differences in hearing preservation for patients treated with stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (FSRT), or hypofractionated stereotactic radiotherapy (hypoFSRT) for VS.

Methods: A retrospective electronic chart review was conducted for all patients with unilateral VS treated with primary RT at a single academic medical center. Primary outcome measure was preservation of serviceable hearing status in the affected ear at last follow-up. Secondary outcomes included tinnitus, vertigo, and imbalance.

Results: 33 FSRT cases, 21 SRS cases, and 6 hypoFSRT cases were identified. Post-operative deterioration in serviceable hearing and tinnitus demonstrated significant differences across cohorts. Hearing retention rates were 69.2% in FSRT patients, 37.5% in SRS patients, and 100% in hypoFSRT patients, which represented the 64.9% of total patients with post-operative serviceable hearing. Five-year tumor control rate was 95.2%, 93.9%, and 100% with SRS, FSRT, and hypoFSRT respectively.

Conclusion: Our series indicated an excellent tumor control rate in all the modalities. FSRT and hypoFSRT cohorts exhibited comparable overall outcomes. Our SRS cohort exhibited increased incidence and shorter time to hearing deterioration compared to FSRT and hypoFSRT cohort. Single fraction SRS was associated with significantly decreased hearing preservation compared to 28 or 5 fraction radiation for vestibular schwannomas

Isaac YANG (Los Angeles, USA)
09:00 - 18:00 #17681 - Stereotactic radiotherapy for large vestibular schwannomas: volume change following radiosurgery versus hypofractionated stereotactic radiotherapy.
Stereotactic radiotherapy for large vestibular schwannomas: volume change following radiosurgery versus hypofractionated stereotactic radiotherapy.

Introduction:

Stereotactic radiosurgery (SRS) is an established treatment option for vestibular schwannomas.[1] Hypofractionated stereotactic radiotherapy (HF-SRT) has demonstrated comparable local control rates, albeit with less long-term follow up.[2, 3] HF-SRT may be an option for larger lesions, potentially increasing the therapeutic ratio. While fractionated SRT can produce more rapid tumor shrinkage compared to SRS [4], there is no published data comparing SRS with HF-SRT with respect to tumor volume reduction over time.

Methods:

A single-institution retrospective review of large (>3.5cc) vestibular schwannomas treated with SRS or HF-SRT was conducted. Patients received either Gamma Knife SRS (GK-SRS) to a dose of 12-13.5 Gy or linac-based HF-SRT to 25Gy in 5 fractions, between 2013 and 2018. Follow-up MRIs were uploaded onto planning software, and individual tumors were contoured to determine volume. These volumes were then calculated as a percentage of original tumor size.

Results:

A total of 33 patients had vestibular schwannomas greater than 3.5cc. Of these, 19 received GK-SRS and 14 received HF-SRT. Median follow-up duration was 16 months for GK-SRS, and 21.5 months for HF-SRT. Mean tumor volume for patients treated with GK-SRS was 4.48cc, and 7.24cc for HF-SRT. At 3-6 months post-treatment, mean tumor size was 100.4% for GK-SRS compared to 97.7% for HF-SRT (p=0.30). At 7-12 months, mean tumor size was 81.6% compared to 77.0% respectively (p=0.34). At 13-18 months, mean tumor size was 88.6% versus 76.8% (p=0.28). There was a significant difference in mean tumor volume between solid lesions (106.5%) and cystic lesions (57.8%) at 13-18 months (p=0.0015). Two patients in the GK-SRS arm required shunt insertion for hydrocephalus. One patient in each arm experienced local failure.

Conclusions:

There was a greater tumor volume reduction within our study period with HF-SRT, though this was not statistically significant. Cystic tumors reduced in volume significantly more than solid lesions.

Michael HUO (Brisbane, AUSTRALIA), Michael HUO, Heath FOLEY, Mark PINKHAM, Catherine JONES, Michael JENKINS, Emma THOMPSON, Sarah OLSON, Bruce HALL, Trevor WATKINS, Matthew FOOTE
09:00 - 18:00 #17525 - “Facial nerve outcomes of Gamma Knife Radiosurgery treating vestibular Schwannomas; Kingdom’s first experience”.
“Facial nerve outcomes of Gamma Knife Radiosurgery treating vestibular Schwannomas; Kingdom’s first experience”.

Objective: Facial nerve weakness is a known surgical complication of treating Vestibular Schwannomas. The study is reported in order to describe facial nerve outcomes with standard dose GK radiosurgery as the first ever experience from the Kingdom.

Methods: The “Perfexion” unit was installed at PSMMC in Sep. 2013. A total of 110 patients have been treated including 26 Vestibular Schwannomas. Patient’s treatment details and course of follow up were collected and updated on Departmental Radiosurgery Database. All the patients were reviewed first in combined Neuro-Oncology meeting to plan course of GK radiosurgery. Baseline Audiometry of all (100%) and Brainstem Auditory Evoked responses (BAER) in selected cases were performed. Patients were assessed and documented for hearing, vestibular and facial nerves (House Brackmann grading) functions during their follow up. SPSS version 24 was used to analyze outcomes.

Results: A total of 26 patients were treated with median age of 48 years (range: 23-78). Female to male ratio; 1.6:1. ZM (Zini Magnan) classification; Stage 1: 19%, Stage 2: 19%, Stage 3: 38.5%, Stage 4: 23.5%. Median marginal dose: 12.5 Gy at 50% isodose line. After a median 26 months follow up (excluding 2 patients who lost to follow up), three-dimensional volume reduction was 20.5% (base line median volume: 1.95cc and at last FU: 1.55 cc). 9/26(34%) had their volumes remained stable. 1 patient had an asymptomatic progression of 3 mm with cystic transformation present. 2 patients had mild asymptomatic hydrocephalus. And all the patients available for follow up did not express Facial nerve weakness beyond G2 HB grading(G1:22/24, G2: 2/24 pts).

Conclusion: Standard GK radiosurgery treatment is considered preferred over surgical approach for saving facial nerve functions.

Bilal MUHAMMAD, Maarouf MAHMOUD ADILI (Riyadh, SAUDI ARABIA), Ali Matar ALZAHRANI, Abdulaziz ALHAMAD, Saleh BAMAJBOUR
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P02
09:00 - 18:00

EPOSTER - 02 AVMs
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17715 - Assessing the volume of large cerebral arteriovenous malformations: Can the ABC/2 formula reliably predict true volume?
Assessing the volume of large cerebral arteriovenous malformations: Can the ABC/2 formula reliably predict true volume?

Background: Stereotactic radiosurgery (SRS) is an important treatment option for preventing intracranial hemorrhage with cerebral arteriovenous malformations (AVMs). Treatment outcome with SRS is volume-dependent, with smaller AVMs having greater rates of obliteration than larger AVMs. The ability to estimate AVM volume has significant value in guiding AVM management and prior studies have focused on relatively small AVMs.

Objective: To determine whether AVM volume measurement calculated from the ABC/2 formula is accurate compared to volume calculated by the computer-assisted planimetric method for large AVMs.

Methods: Retrospective review of 37 patients with 42 intracranial AVMs >3cm in diameter that underwent treatment with dose-hypofractionated stereotactic radiotherapy (HSRT) from 2001 to 2018. Two raters independently measured pre- and post-HSRT volumes by ABC/2 formula and computer-assisted planimetry in a blinded fashion. Inter-rater reliability was assessed by calculation of intra-class correlation coefficient (ICC). Volumes were compared using paired t-tests, Pearson correlation, linear regression, and Bland-Altman plot analyses.

Results: The ICC between the 2 raters for planimetric and ABC/2 volumes was .859 and .799, respectively. ABC/2 volumes (mean = 28.6 cm3) were significantly smaller than planimetric volumes (mean = 26.1 cm3) (P = 0.008). Strong correlation was seen between the two methods using both linear regression (R2 = 0.904) and Pearson correlation (r = 0.951, p <0.001) analyses. The percent volume change following HSRT was significantly different between the two methods (P = 0.009). 

Conclusion: The ABC/2 and planimetric methods are reproducible for measuring cerebral AVM volumes. Volume estimation using the ABC/2 formula underestimates planimetric AVM volume, and has limited clinical utility.

Alon KASHANIAN (Los Angeles, USA), Hiro SPARKS, Tania KAPREALIAN, Nader POURATIAN
09:00 - 18:00 #17526 - AVM’s radiosurgery outcomes from the first Gamma Knife experience in KSA.
AVM’s radiosurgery outcomes from the first Gamma Knife experience in KSA.

Objective: To review outcomes of radiosurgery in previously embolized AVMs as a first experience in the kingdom.

Methods: Gamma Knife Perfexion system was installed at PSMMC in September 2013. A total of 110 patients including 24 Arteriovenous Malformations have been treated. The data has been documented in a prospective radiosurgery database. All the AVMs were treated by a team of professional Interventionists, Radiation oncologists, Neurosurgeons and Physicists. All treated cases remain on follow up with interval reassessment through MRI and yearly Angiograms. SPSS version 24 was used to analyze outcomes.

Results: A total of 24 patients underwent radiosurgery with same day MRI and Angiogram co- registration. Males: 15, Females: 9. Mean age was 36 years. Mean number of past embolizations: 1.33.

Brain site involvement: Temporal lobe: 7(29%), Frontal and occipital lobes: 5(21%)each, Parietal lobe: 4(17%), and 1 case(4%) each for cerebellar, midbrain and thalamic AVMs.

Spetzler-Martin grading; G2: 3(12.5%), G3: 12(50%), G4: 8(33.3%), G5: 1(4.2%). Response; CR: 8/17 evaluable patients (47%), PR: 7/17(41%), No response: 2/17(11%). Objective response rate: 88%. Median Follow up: 23 months.

7 patients did not complete their one year follow up yet. Non-responding patients underwent combination of surgery and further embolizations. 2 patients underwent partial volume treatment due to large size of AVM. Volume based Radiosurgery median dose: 18 Gy. Post radiosurgery bleed: none.

Conclusion: Gamma knife Radiosurgery is an effective treatment modality for medium to large AVMs. Radiosurgery reduces risk of bleeding without causing major complications.

Bilal MUHAMMAD, Abdulaziz ALHAMAD, Maarouf MAHMOUD ADILI (Riyadh, SAUDI ARABIA), Saleh BAMAJBOUR, Riyadh OKAILI, Maher HIJJI
09:00 - 18:00 #17848 - Excellent outcomes with frameless linear accelerator radiosurgery for arteriovenous malformations with 3D catheter angiographic planning and conservative patient selection.
Excellent outcomes with frameless linear accelerator radiosurgery for arteriovenous malformations with 3D catheter angiographic planning and conservative patient selection.

Introduction

 

Patients with brain arteriovenous malformations (AVMs) can be treated with observation, surgery, embolization or radiosurgery. Since the publication of the ARUBA trial there has been increased concern that the risks of interventional treatment such as surgery or radiosurgery may exceed the benefits for unruptured AVMs. Our series shows that radiosurgery remains safe and highly effective for carefully selected and planned small AVMs.

 

Methods

 

During the period 2010-2018, radiosurgery treatment for 31 AVMs in 30 patients was administered at our centre. All patients underwent frameless radiosurgery with a Novalis Tx radiosurgery system incorporating a 6D robotic couch and the BrainLab Exactrac system for frameless positioning and a Varian linear accelereator with a micro multi-leaf collimator. In all cases catheter based angiography was performed prior to the treatment and the 3D rotational non-subtracted images were incorporated into the planning.

 

Results

 

The average age was 40 at time of radiosurgery. 17/31 patients (55%) had a history of haemorrhage. Average AVM volume was 1.27cc (range: 0.131 – 3.499 cc). Median prescription isodose was 20Gy (range 15-22Gy) prescribed to the 70% isodose in the vast majority of patients. The mean modified Pollock-Flickinger score was 1.116 (range 0.46-1.96). 16/31 (52%) were Spetzler-Martin Grade 3.

 

Two patients were lost to follow up. Of patients who are 2 years or more post radiosurgery the AVM obliteration rate was 100% (21/21) confirmed by DSA or MRA.

No patient experienced a post SRS haemorrhage during 93 patient years of follow-up.

One patient (3%) experienced a worsening of neurological deficit with mild lower limb paresis after SRS for an internal capsule AVM that had presented with haemorrhage.

 

Discussion and Conclusions

 

In small carefully selected and planned AVMs treated with frameless radiosurgery 97% of patients with minimum 2 years follow up have achieved AVM obliteration without new neurological deficit.

Benjamin JONKER (Sydney, AUSTRALIA), Nitya PATANJALI
09:00 - 18:00 #17022 - Gamma Knife Radiosurgery: The Gold Standard Treatment for Intracranial Dural Arteriovenous Fistulas without Cortical Venous Drainage.
Gamma Knife Radiosurgery: The Gold Standard Treatment for Intracranial Dural Arteriovenous Fistulas without Cortical Venous Drainage.

Context: Endovascular therapy is currently the most common treatment approach for intracranial dural arteriovenous fistula (DAVF), followed by microsurgery. Gamma Knife radiosurgery (GKS) is usually reserved as the last modality of treatment of intracranial DAVF.

 

Aim: To evaluate the clinical and radiological outcome of GKS in the treatment of DAVF without CVD.

 

Methods and Material: This series includes patients who underwent GKS for intracranial DAVF without CVD over 10 years (Jan 2007 to Dec 2016) in All India Institute of Medical Sciences, New Delhi. Their demographic profile, clinical presentation, imaging details, GKS details and follow up clinical status was obtained retrospectively. Clinical follow up, along with radiological assessment using MRI every 6 months was done after GKS. DSA was performed once MRI strongly suggested obliteration of DAVF. Patients who had a clinical follow up of less than 1 year were excluded from the study.

 

Results: 5 patients (4 males and 1 female) who had DAVF without CVD were included the study. The mean age was 44.8 years. All patients had complete obliteration of fistula on digital subtraction angiography (DSA) at a mean duration of 24 months post GKS. All patients had complete resolution of symptoms at the last follow up.

 

Conclusions: Gamma Knife surgery is the most effective and the safest treatment modality for dealing with DAVFs without CVD. Instead of reserving it as the last resort for patients with DAVF without CVD, it should be considered as the gold standard treatment for DAVFs without CVD.

Hardik SARDANA (New Delhi, INDIA), Deepak AGRAWAL
09:00 - 18:00 #17775 - Impact of high dose GammaKnife radiosurgery on control of AVM; review of single center in Saudi Arabia.
Impact of high dose GammaKnife radiosurgery on control of AVM; review of single center in Saudi Arabia.

Introduction: AVM is uncommon problem however it’s management usually including either surgery, embolization or radiotherapy. Radiosurgery is an efficient method of treatment even though there’s a lot of variation in the literature about it’s outcome.

 

Method: we conduct a chart review for 21 patients diagnosed with AVM been treated at Prince Sultan Military Medical City (PSMMC)using gammaKnife radiosurgery (GK-RSR) regardless if they received any previous treatments.  We used high dose (18-22 Gy/1 fx depends on the initial size of the lesion).  We assessed the response of the treatment by systemic review, clinical examination and imaging.

 

Results: among of 21 patients unfortunately 2 of them no available records  follow/up after KG-RSR. The  rang of follow/up  was (62-2134 days) with average of  839.4 days. 9 patients (47%) developed 100% response clinically & radiologically. 8 patients (42.10%) were clinically stable with >75% radiologically response. 2 patients (10.5%) unfortunately had <75% response radiologically with partial clinical response.

 

Conclusion: Gk-RSR is very efficient especially for those who didn’t respond very well for other modalities of treatment.

Bilal MOHAMMED, Ma'aroof ADILLI, Abdulaziz ALHAMAD (Riyadh, SAUDI ARABIA)
09:00 - 18:00 #17776 - Predictors of Adverse Radiation Effect with a Volume Staged Radiosurgical Approach: A Multi-Institutional Study.
Predictors of Adverse Radiation Effect with a Volume Staged Radiosurgical Approach: A Multi-Institutional Study.

Abstract

Background

Volume-staged stereotactic radiosurgery (VS-SRS) provides an effective option for large arteriovenous malformations, but optimizing treatment for these recalcitrant and rare lesions has proven difficult and there are no reports of predictors of adverse radiation effect with a volume-staged approach in the literature.

 

Methods

This is a multi-centered retrospective review of patients treated with a planned prospective volume staging approach to stereotactically treat the entire nidus of an AVM with volume stages separated by intervals of 3-6 months. A total of 9 radiosurgical centers treated 257 patients with VS-SRS between 1991 and 2016. We evaluated transient and permanant symptomatic adverse radiation effects (ARE). Neurologic status was graded as improved, declined, or stable.

Results

With a median age of 33 years old at the time of first SRS volume stage, patients received 2-4 total volume stages and a median follow up of 5.7 years after VS-SRS. The median total AVM nidus volume was 23.25 cc (range: 7.7-94.4 cc) with a median margin dose per stage of 17 Gy (range: 12-20 Gy). The volume per stage ranged from 1.9-62.9 cc (median 11.5 cc) in the initial stage and 0.8-47.2 cc in the second volume stage (median 9.7 cc). A total of 74 patients experienced at least one event of ARE. Transient ARE events occured in 66 cases and permanant ARE deficits occured in 31 events. The most common event was headache occuring in 21 patients. Deep draining venous structure, larger total AVM volume, larger V12 per stage, larger summated V12 Gy, larger volume per stage, and increasing the number of isocenters per stage were all associated with increased risk of ARE. Of available AVM scores, only modified RBAS was associated with ARE (Hazard Ratio 1.526, 95% Confidence Interval 1.279-1.820).

 

Conclusion

VS-SRS is an option for upfront treatment of large AVMs. Higher dose per stage reported here was not associated with increased rates of ARE. However, larger volumes per stage, larger lesions, and higher volumes of V12 Gy were associated with risk of ARE suggesting a continued dissociation between treatment volume and dose with a volume-staged approach. Smaller volumes per stage with higher gradient indexes may be associated with reduced risk of ARE.  

Zachary SEYMOUR, Jason CHAN (San Francisco, USA), Penny SNEED, Hideyuki KANO, Rachel JACOBS, Judith HESS, Craig LEHOCKY, Veronica CHIANG, Jason SHEEHAN, Tomas CHYTKA, Dale DING, Anthony KAUFMANN, Caleb FELICIANO, Cheng-Chia LEE, John LEE, Roman LISCAK, Brendan MCSHANE, Hong YE, Huai-Che YANG, Samuel SOMMARUGA, Rafael RODRIGUEZ-MERCADO, Inga GRILLS, Micheal MCDERMOTT
09:00 - 18:00 #17699 - Radiation induced change after Gamma knife radiosurgery for cerebral arteriovenous malformation.
Radiation induced change after Gamma knife radiosurgery for cerebral arteriovenous malformation.

Object

Radiation induced change (RIC) on magnetic resonance image after Gamma knife radiosurgery (GKRS) for cerebral arteriovenous malformation (AVM) is not rare. We reviewed the patients who underwent GKRS for AVM and analyzed the results and factors associated with RIC.

Material and method

We reviewed 251 patients who underwent GKRS for AVM from October 2010 to August 2016. All the patients were followed up at least 3 years. Males were 140 and females were 111. Pediatric patients were 44 and adults were 207. Mean age of the patients was 33.91(range: 4.21-72.00). Six patients had undergone pre-GKRS embolization. One hundred and twenty three patients had ruptured AVMs and 128 had unruptured ones. We analyzed the obliteration rate and RIC occurrence rate. The factors such as sex, age, diameter of lesion, lesion volume, treatment volume, ruptured or not, isodose, marginal dose, maximal dose, and pre-GKRS embolization or not were analyzed to figure out the influence of obliteration and RIC occurrence.

Results

Overall obliteration rate was 64.94% (163/251) at final follow-up. Actuarial obliteration rate at 36 months after GKRS was 69.2%. Overall RIC occurrence rate was 42.63% (107/251) and actuarial RIC occurrence rate was 21.2% at 24 months after GKRS. There were no statistical differences between pediatric patients and adult ones. Obliteration rate showed statistically significant difference according to marginal dose (p=0.01) and maximal dose (p<0.01). RIC occurrence rate was statistically related to large lesion volume (p<0.01, r=0.37), large treatment volume (p<0.01, r=0.40), low marginal dose (p=0.04, r=0.32), and unruptured AVM (p<0.01, r=0.39). All other factors were not statistically significant.

Conclusions

Obliteration rate after GKRS for AVMs were comparable with the results from other reports. RIC was not rare findings after GKRS for AVMs. However most of the patients showed no significant clinical symptoms. In this study, there could be higher RIC occurrence in large AVMs, and unruptured ones.

Hae Yu KIM (Busan, KOREA), Sun-Il LEE
09:00 - 18:00 #17676 - Radiosurgery as a salvage therapy for refractory or difficult to treat intracranial dural arteriovenous malformations.
Radiosurgery as a salvage therapy for refractory or difficult to treat intracranial dural arteriovenous malformations.

Introduction:Dural arteriovenous fistulas (dAVFs) are primarily treated with endovascular therapy. However, stereotactic radiosurgery (SRS) is a viable alternative strategy when endovascular therapy is not possible or when it fails to achieve either angiographic occlusion or symptomatic relief. We examined our single-institution experience treating refractory dAVF with SRS.

Methods:An institutional database was searched for patients treated with linear accelerator based SRS for dAVF after failed endovascular therapy with more than one-year follow up. We specifically examined patient and treatment characteristics and outcomes (angiographic and symptomatic) with an emphasis on determining how radiosurgery can be used as a salvage after failed endovascular therapy.

Results:Ten patients, 6 men and 4 women, average age 48.2 (range 4-57), were treated with 13 SRS sessions. All patients had undergone one or more attempts at endovascular occlusion. Average follow up was 67.9 months. One patient suffered from recurrent fistulas in different regions of the posterior fossa and required 3 treatments. Another patient’s fistula was large enough that we treated her in two separate sessions. The remaining patients were treated in a single session. Treatment volumes ranged from 0.6 cc to 28.1 cc, average 5.38 cc. Median SRS dose was 1953 Gy (range 1600-2400 Gy) delivered by dynamic conformal arcs in 8 patients and by intensity modulated therapy in two patients. There was  one serious complication, the patient requiring three treatments developed radiation necrosis requiring surgery for diagnosis and treatment. One other patient with presenting symptoms of seizure and headache continued to require ongoing treatment for both symptoms despite angiographic occlusion of her fistula. Six patients have angiographic confirmed occlusion of their fistula. The remaining 4 have decreased fistula size on computed tomographic angiography but not occlusion. 

Conclusions:SRS is a reasonable treatment modality for refractory or difficult to treat dAVF with an acceptable complication rate and good treatment success.

Randy L. JENSEN (Salt Lake City, USA), Phillip TAUSSKY, Dennis C. SHRIEVE
09:00 - 18:00 #17695 - Radiosurgery in Giant AVMs, wich is the best option?
Radiosurgery in Giant AVMs, wich is the best option?

The tretament of big AVMs still remaind a challenge for the neurosurgeon and radiosurgeon. Surgery is difficult and the embolization is recomendet as an preeliminary treatment to help the surgery and radiosurgery.The old experience in the treatment of big AVMs is based in stage dose Radiosurgery, low dose and after one or two years another low dose, latter we beagn to use the consept of stage volume radiosurgery. Stage volumen SRS means to separete in two volumen the AVM and to treated in to times with high therapeutic dose. The introduction of Cyberknife make posible to use onother concept of tretament ,Hypofractionation. There is a big discusion about which is the best option and if we have to use surgery or embolization.

We treat in our department 1010 patient, 20% of tham big AVMs, we use all the method we plan and in pur opinion the more eficient way are stage volumen and Hypofractination ( 2x10 Gy) The previous embolization did not use us in the early AVM oclusion, we strongly belive that we don-t need previous embolization. We can use it only in high flow AVMs. Syrgery was needed in some special cases

Kita SALLABANADA DIAZ (Madrid, SPAIN), Rafel GARCIA, Iciar SANTAOLALIA
09:00 - 18:00 #17734 - Stereotatic radiosurgery for arteriovenous malformations after endovascular embolization.
Stereotatic radiosurgery for arteriovenous malformations after endovascular embolization.

Microsurgery, embolization or stereotactic radiosurgery (SRS) can be used, both individually or in combination with each other for AVM treatment. Nidus volume is one of the factors that is crucial for predicting the control of AVM. Combined treatment approach with endovascular embolization followed by SRS can help to reduce the SRS target volume.

 The aim of the work is evaluation safety and feasibility of this aproach.

Methods and Materials: 8 patients with AVM after previous endovascular treatment underwent SRS on the CyberKnife M6 from 2016 till 2018 at the Sigulda Hospital, Stereotactic radiosurgery Centre. The mean age of patients was 32.5 [95% CI [23.5-37.8]. 6 patients had history of previous hemorrhage from AVM. All 8 patients had incomplete endovascular AVM Onyx embolization prior to radiosurgery. Patients were divided into 2 groups depending of the volume of AVM: small AVM 10 cm3 - 6 patients.

Single-fraction CyberKnife SRS was performed in 2 patients at a dose of 20 Gy, 6 patients had hypofractinated SRS (2 fractions, a total dose of 24 Gy).

Results: Patients undergo a radiological examination (MRI and MRI angiography) after the treatment. Patients had no signs of repeated bleeding from AVM after SRS. Digital subtraction angiography (DSA) was performed for 2 patients, who were 18 and 24 months after CyberKnife SRS. Both patients had signs of complete obliteration of AVM. No one patient had signs of postradiation toxicity grade 2-3. 4 patients had brain edema in the follow-up MRI, that after medication resolved later.

 Conclusions: The combined endovascular/SRS approach is safe, in terms of post-SRS hemorrhage, or post-radiation toxicity. However, the assessment of statistically reliable levels of obliteration requires further observation and research.

Vladyslav BURYK (Sigulda, LATVIA), Maris MEZECKIS, Mirza KHINIKADZE, Dace SAUKUMA, Jelena NIKOLAJEVA, Maris SKROMANIS
09:00 - 18:00 #17712 - Treatment of large arteriovenous malformations with dose hypofractionated stereotactic radiation therapy: an institutional experience.
Treatment of large arteriovenous malformations with dose hypofractionated stereotactic radiation therapy: an institutional experience.

Background: Brain arteriovenous malformations (AVMs) are pathologic tangles of intracerebral vessels. Treatment of AVMs aims to reduce the risk of devastating intracranial hemorrhage (ICH). Dose hypofractionated stereotactic radiation therapy (HSRT), can be used to treat large lesions while reducing the risk of radiation toxicity to surrounding structures. We describe a study of our institutional experience over the last fifteen years in treating large AVM’s with both five- and six-fraction HSRT and evaluate pre-treatment characteristics that are most predictive of radiographic response.

Methods: 37 patients and 42 treatments for intracranial AVMs measuring >3cm in their largest dimension were included.  Data was collected retrospectively using review of electronic health records. AVM volume was measured prior to HSRT with LINAC and at the patient’s most recent follow-up appointment. Symptomatic outcomes, including treatment-related inflammation, were measured and defined categorically.

Results: Complete obliteration was achieved in 11.9% of patients. Mean AVM volume reduced significantly after HSRT (P=8.7e-8). Percent volume reduction differed significantly between patients receiving 30Gy fractions, (∂V=-48.7%), and 25Gy fractions (∂V=-29.1%), (P=0.035).  Patients with partial or complete obliteration were more likely to receive a total dose of 30Gy rather than 25Gy (P=0.056), and trended toward being treatment naïve (P=0.053).

Conclusion:  HSRT may be used as a means to manage large AVMs, with obliteration in some cases and sufficient volume reduction in most others for adjuvant treatment with other modalities.  30Gy total dose was generally superior to 25Gy in achieving significant complete or partial obliteration. Further studies focused on longer follow-up periods are warranted.

Hiro SPARKS, Arev HOVSEPIAN, Bayard WILSON, Antonio DESALLES, Michael SELCH, Alon KASHANIAN (Los Angeles, USA), Tania KAPREALIAN, Nader POURATIAN
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P03
09:00 - 18:00

EPOSTER - 03 Functional
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17741 - Clinical Outcomes Following Linac-Based Radiosurgery for Trigeminal Neuralgia.
Clinical Outcomes Following Linac-Based Radiosurgery for Trigeminal Neuralgia.

Objective: Radiosurgery is a reliable and safetreatment option for trigeminal neuralgia. Nevertheless, precise and accurate targeting is critical to optimize outcome after radiosurgery for trigeminal neuralgia (TN). We reviewed clinical outcomes and complications following frame-based versus frameless stereotactic radiosurgery using a linear accelerator (linac) based treatment device, with radiation collimated using 4mm versus 5mm diameter cones in patients with medically refractory, intractable TN. 

Methods: We performed a retrospective review of all patients who underwent stereotactic radiosurgery for TN at our institution between 1996 and 2018. The Barrow Neurological Institute (BNI) pain score was used to evaluate pain relief.

Results: A total of 282 patients were identified. Their mean age at the time of radiosurgery was 68.1 years (range, 24.3 – 95.5 years). A total of 119 (42.2%) patients underwent radiation collimated by 4mm cones, whereas 5mm cones were used in the remaining 163 (57.8%) patients. Overall, frameless stereotaxy was used in 112 (39.7%) patients. Statistically significant differences in demographic parameters amongst groups were observed for preoperative BNI pain scores and age (p<0.005). Following radiosurgery, 67.5% of patients in the 5mm group experienced complete pain relief (BNI I), compared to 40.3% in the 4mm group (p<0.005). A complete pain relief was achieved in 42.0% of cases in the frameless group, and in 65.3% in the frame-based group (p<0.005). Overall, mean latency to initial pain relief was 1.1 months. Pain recurrence occurred overall in 15.6% of cases. A higher frequency of pain recurrence was present in the 4mm and the frameless group (28.6%) (p<0.005). Side effects of SRS treatment included permanent facial hypoesthesia in 5% (n=14), hyperesthesia/paresthesia in 2.5% (n=7), dry eye syndrome in 1.8% (n=5) and deafferentiation pain in 5.7% (n=16). 

Conclusion: Frameless radiosurgery with a 5mm collimator, is a feasible treatment option for patients with TN, avoiding the complications and hindrances associated with rigid head frame fixation without compromising clinical safety or outcomes. Despite the risk of spillage-related brainstem adverse effects of larger collimator size, confirmed our results, that a 5mm collimator is superior to 4mm collimator size in terms of pain relief, with no increase in long-term side effects. 

Jenny KIENZLER, Nader POURATIAN (Los Angeles, USA), Won KIM, Kaprealian TANIA
09:00 - 18:00 #17774 - Cyberknife treatment of medically intractable Trigeminal Neuralgia: A comparison of the outcomes between isocentric and non-isocentric treatment planning techniques.
Cyberknife treatment of medically intractable Trigeminal Neuralgia: A comparison of the outcomes between isocentric and non-isocentric treatment planning techniques.

Introduction: The efficacy of using SRS to treat medically intractable trigeminal neuralgia is well established.  When treating with CyberKnife®, some practitioners like to use an isocentric strategy and others advocate irradiating a portion of the cisternal segment of the nerve in a non-isocentric manner. Both strategies aim to optimize the success of the treatment and mitigate facial numbness as the potential side effect.

 

Objective: This abstract compares the treatment outcome of these two strategies.

 

Method: We retrospectively reviewed 81 patients from 2009-2017 in our treatment data base.  The non-isocentric technique was used for treating 40 patients, while the isocentric technique was used to treat 41 patients.  The efficacy in pain control and the occurrence of facial numbness were analyzed.

 

Results: The median follow up was 68 months. For the non-isocentric treatments the median prescription dose was 60 Gy (80% isodose line) and median target volume was and 0.069 cc.   For isocentric treatments the median prescription dose was 85 Gy (100% isodose) and median volume of nerve receiving 60 Gy was 0.033 cc. Of the 81 patients, 69 (85%) patients responded to the treatment (Barrow Neurological Institute BNI pain score equal to or below 3). There is no difference when comparing the two strategies (80.0% and 90.2% in isocentric and non-isocentric respectively, p=0.2). The number of patients with symptomatic facial numbness in both groups was 13 (16%), 8 (20%) in the non-isocentric group and 5 (12%) in the isocentric respectively.

 

Conclusion: We found no significant difference in the outcome in treating TN with isocentric and non-isocentric paradigm.   

Victor TSE (Redwood City, USA), Christopher MCGUINNESS, Ming TENG, Amy GILLIS, Laura MILLENDER, Minn YURI, Anand KRISHNAMURTHY, William SHERIDAN, Adler JOHN
09:00 - 18:00 #17903 - Gamma knife thalamotomy (GKT) for essential tremor (ET).
Gamma knife thalamotomy (GKT) for essential tremor (ET).

Abstract  07 SRS 

Gamma knife thalamotomy (GKT)  for essential tremor (ET)

E.Larrachea,  J.Lorenzoni, F.Bova, M.Henriquez, P.Navarrete, C.Luhr, G. Zomosa

Gamma knife Chile, Santiago de Chile.

Intruduction : There are several ET patients specially older yhat are medically refractory, fot those we propose to perform GK thalamotomy.                                                                                                    Objectives : To relieve ET in medically refractory patients.                                                                                                                                                                                                                            Material and Methods : We presen our experience using GKT for the treatment of medically refractory ET .Nine ET patient underwent GKT. High resolution magnetic resonance imaging guidance was used for Ventral Intermedius nucleus (Vim) targeting. A single  4 mm isocenterwas used to  target a maximum dose of 130 Gray to the Vim. Pre and post treatment clinical evaluation was performed using Global (A+B+C)  Fahn Tolosa Marin tremor rating scale (FTM) .                                                                                                                                                                                                                              Results :The mean patient age was  68,2 years (57-80) with a mean  follow-up of 36 months (12-60). In seven  patients (78%) an important clinical improvement was observed ( mean pre-treatment FTM= 35.5 and mean post  treatment FTM=16.5) . In one patientno significant effect was observed and a second GKT was performed achieving a FTM score improvement from 28.9 to 11.5. One patient present edema in the Vim target  and remitted with corticosteroids.                                                                                                                                                                                                                                      Discussion and Conclusion : GKT could be considered as an effective and safe  neurosurgical  treatment for medically refractory  ET  and also  is elegible  for older patients over  seventy years.

Keywords . Essential tremor, thalamothomy, gamma knife radiosurgery.

Eduardo LARRACHEA , Jose LORENZONI, Marcos HENRIQUEZ, Francisco BOVA, Claudio LUHR, Gustavo ZOMOSA (santiago de Chile, CHILE)
09:00 - 18:00 #17784 - High single dose of Radiotherapy using Gamma-Knife is efficient treatment for Trigeminal Neuralgia either mono or combined with other modality . single institute retrospective review.
High single dose of Radiotherapy using Gamma-Knife is efficient treatment for Trigeminal Neuralgia either mono or combined with other modality . single institute retrospective review.

Introduction: Trigeminal Neuralgia (TN) is serious problem with poor response to RSR  ≤75Gy, Fractionated radiotherapy, local nerve anesthesia or medicine.  Some literature showed that high dose single fraction radiotherapy maybe a effective choice.

 

Method: we conduct a retrospective review for 13 patients of TN been treated at Prince Sultan Military Medical City (PSMMC) by single fraction of Gamma-Knife radiosurgery (GK-RSR)80Gy/100% or above, between (11/4/2013 till end of December 2017). These patients had been followed up by history, physical examination & phone call assessment going over symptoms of pain control, need further methods for control of TN and using pain killers or no.

 

Results: among all 13 patients one received 75Gy/100%, another one received 85Gy/100% while the rest received 80Gy/100%. The average of follow/up was 1058 days after receiving the GK-RSR. 8 patients (61.5%) achieved 100% response, 3 patients (23.10%) achieved ≥75% response & 2 patients (15.4%) achieved 25-75% response. Regarding the pain score within 3-6 months post therapy was as following 0 patients (0%) had a score of >7, 8 patients (61.5%) had a score of ≥4-≤7 and 5 patients (38.5%) had a score of <4. Regarding continuity of using pain killers; 9 patients (69.20%) are still using pain killers regularly in contrast to 4 patients (30.80%) stop using pain killers. 4 patients (30.80%) needed further therapy including (radiotherapy & nerve block).

 

Conclusion: high dose ≥ 80Gy/100% is very effective treatment for TN. With minority of them would need to go for further therapy. With good patient satisfaction

Abdulaziz ALHAMAD (Riyadh, SAUDI ARABIA), Ma'aroof ADILLI, Abdullah ALRUSHOUD, Bilal MOHAMMED, Maher AL HEJJI, Jamal ABDULLAH
09:00 - 18:00 #17825 - Sphenopalatine Ganglion Landmarks for treatment of Facial Dysautonomia.
Sphenopalatine Ganglion Landmarks for treatment of Facial Dysautonomia.

Introduction:Cluster headache (CH) is the most common trigeminal autonomic headache. It remains a medical management challenge. Gamma Knife Radiosurgery (GKR) has been described as a non-invasive alternative treatment. Landmarks for the targeting of the sphenopalatine ganglion still remain obscure, mostly in the Magnetic Resonance Imaging. 

Objective and Methodology:To describe the anatomical characteristics of the sphenopalatine ganglion target using the Gamma Knife, Perfexion model (Elekta AB). 

Case report:A 55-year-old female patient from Angola had been diagnosed with CH for over 10 years, with severe pain on the right hemicranium, progressive worsening, reaching three monthly crises, causing important limitation of her daily routine. MRI showed no abnormalities. Extensive drug regimens and botulin toxin failed to relieve her symptoms. Initially, an anesthetic block of the sphenopalatine ganglion was performed, providing temporary relief. Next, radiofrequency ablation of the ganglion was performed with the sphenopalatine fossa being targeted by fluoroscopy. She returned to Angola obtaining relief for one year, when pain recurred. Therefore we offered the option GKR. The procedure was performed using MRI and CT for targeting. The entire sphenopalatine fossa had a volume of 3.44 cm³ being covered with a single isocenter of 4 mm collimator. Uneventful GKR with dose of 90 Gy to 100% of isodoseline was accomplished. Treatment duration was 50 minutes. The patient was discharged on the same day. She has reported since control of her pain with rare episodes of pain controlled with common analgesics.  

Conclusion:Radiosurgery represents a therapeutic option for patients with CH refractory to medical therapy. It is attractive as a minimally invasive approach without hospitalization and low morbidity for patients who have already failed a multitude of treatments. Bone landmarks seen on CT offer a corridor limiting soft tissue assuring, together with the MRI, safe targeting of the sphenopalatine ganglion.

Aline Lariessy CAMPOS PAIVA (Sao Paulo, BRAZIL), Alessandra GORGULHO, Bruno Henrique DALLO GALLO, Rafael COSTA LIMA MAIA, Juliete MELO DINIZ, Crystian Willian CHAGAS SARAIVA, Antonio DE SALLES
09:00 - 18:00 #17655 - Stereotactic linac radiosurgery in the treatment of trigeminal neuralgia: dosimetric evaluation and long-term follow-up.
Stereotactic linac radiosurgery in the treatment of trigeminal neuralgia: dosimetric evaluation and long-term follow-up.

Objective: To evaluate long-term outcomes and report dosimetric parameters for patients with trigeminal neuralgia treated with linear accelerator (LINAC)-based cone radiosurgery over a 15-year period from a single institution.

 Methods: We conducted a retrospective single-institution review of 68 trigeminal neuralgia (TN) patients treated between 2003 and 2018. All patients were planned with a 5 mm diameter cone using SRS on a LINAC delivered with 4-6 non-coplanar arcs. A dose of 40 Gy was prescribed to the 50% isodose line with the goal of 80 Gy to the isocentre within the trigeminal nerve root and limiting the abutting brainstem dose to 40 Gy. Dosimetric information extracted from the plans was examined for: (i) maximum brainstem dose (ii) mean volume of hippocampus receiving 10 Gy (iii) cranial nerve VII-VIII (CNVII-VIII) maximum dose. Maximum dose was defined as the dose received by a volume of 0.05 cc. The primary outcomes were treatment response and treatment success was defined by the Barrow Neurological Institute (BNI) pain scores ranging I-IIb and I-IIIa, respectively. A Kaplan-Meier (KP) analysis was also conducted.

 Results: Based on the most recent follow-up data, overall treatment response and success rates were 84% (57/68) and 69% (47/68), with approximately 30% no longer requiring medication (22/68).  From the KP analysis, the actuarial probabilities of maintaining pain relief at 1, 5 and 10 years were 89.1%, 54.6% and 47.8 %. The maximum dose to the nerve was 79.5 ±1.7 Gy. A strong consistency in the plan dosimetry was observed for all 68 patients with a maximum brainstem dose of 32.7 ±4.0 Gy, the volume of hippocampus receiving 10 Gy was 0.04 ±0.08 cm3, and the maximum dose to the CNVII-VIII was 7.0 ±4.5 Gy.No patients suffered symptomatic brainstem or other late radiation injuries.  

 Conclusion: Doses to the nerve, brainstem, hippocampus and CNVII-VIII are shown to be consistent; however, further analysis will explore if there are subtle differences in dosimetry between responders and non-responders. Therefore, LINAC SRS is a safe and effective treatment for long-term TN pain control with results similar to those reported using other SRS techniques, such as Gamma Knife. It should be considered a favorable treatment option for both untreated cases and for recurrent pain following other treatment modalities. 

Nicolas P PLOQUIN (Calgary, CANADA), Scott AGNEW, Alana HUDSON, Robert NORDAL, Shaun LOEWEN, Zelma Ht KISS
09:00 - 18:00 #17823 - Treatment of Glossopharyngeal Neuralgia with Gamma Knife.
Treatment of Glossopharyngeal Neuralgia with Gamma Knife.

Introduction: Glossopharyngeal neuralgia is a rare condition of difficult diagnosis and medical management. Gamma Knife Radiosurgery (GKR) may represent an excellent minimally invasive treatment with similar to microsurgery results. 

Objective and Methodology:To discuss the GKR treatment of glossopharyngeal neuralgia. 

Results: A 59-year-old male presented in 2012 with change in voice tone and severe pain in the left hemi-face. It had worsened over five-years with painful sudden irradiation to the left ear, cough and difficulty swallowing.   Magnetic Resonance (MRI) showed the vagus-glossopharynngeal complex on FIESTA/CISS sequencing, as well as an artery at bulbar nerves exit, dividing the complex. Glossopharyngeal neuralgia with failed medical therapy was established after side effects of high doses of Carbamazepine and 12-sessions of trans cranial magnetic stimulation. Pain continued worsening, interfering in his daily routine. GKR was performed targeting the medial cisternae segment of the glossopharyngeal nerve (volume of 3.44 cm³) with a prescription dose of 90 Gy, 100% isodose site. The patient was discharged on the same day, now 5 months after the procedure he reported pain improvement. 

Conclusion: Gamma Knife Radiosurgery becomes an excellent alternative for the treatment of glossopharyngeal neuralgia. The targeting has varied in the small literature series, although the mid-cistern portion of the nerve is considered the safest and well contrasted from the CSF using MRI FIESTA/CISS sequencing.

Aline Lariessy CAMPOS PAIVA (Sao Paulo, BRAZIL), Antonio DE SALLES, Juliete MELO DINIZ, Bruno Henrique DALLO GALLO, Anderson MARTINS PÁSSARO, Alessandra GORGULHO
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P04
09:00 - 18:00

EPOSTER - 04 Gliomas
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17748 - 11C-methionine positron emission tomography for target delineation of newly diagnosed and recurrent glioblastoma in radiation therapy planning.
11C-methionine positron emission tomography for target delineation of newly diagnosed and recurrent glioblastoma in radiation therapy planning.

PURPOSE: The purpose of this work was to define the optimal margins for gadolinium-enhanced T(1)-weighted magnetic resonance imaging (Gd-MRI) and T(2)-weighted MRI (T(2)-MRI) for delineating target volumes in planning radiation therapy for both newly diagnosed and recurrent glioblastoma multiforme (GBM) by comparison to carbon-11-labeled methionine positron emission tomography (MET-PET) findings.

Materials and Methods: Computed tomography (CT), MRI, and MET-PET were separately performed for radiation therapy planning for 32 newly diagnosed and 25 recurrent patients with GBM over the course of 2 weeks. Among the MRI scans, we used the contrast-enhanced T1-weighted images (Gd-MRI) and T2-weighted images (T2-MRI). The Gd-MRI-based clinical target volume (CTV) (CTV-Gd) and the T2-MRI-based CTV (CTV-T2) were defined as the contrast-enhanced area on Gd-MRI and the high intensity area on T2-MRI, respectively. We defined CTV x mm (x = 5, 10, 15, 20) as x mm outside the CTV. MET-PET-based CTV (CTV-MPET) was defined as the area of accumulation of MET-PET. We calculated the sensitivity and specificity of CTV-Gd and CTV-T2 following comparison with CTV-MPET, which served as the gold standard in this study.

Results: In newly diagnosed patients, the sensitivity of CTV-Gd (20 mm) (86.4%) was significantly higher than that of the other CTV-Gd. The sensitivity of CTV-T(2) (20 mm) (96.4%) was significantly higher than that of the other CTV-T(2) (x = 0, 2, 5, 10 mm). The highest sensitivity and lowest specificity was found with CTV-T(2) (x = 20 mm). In recurrent patients, the sensitivity of CTV-T2 5 mm (98%) was significantly higher than CTV-T2 (87%), and there was no significant difference in the sensitivity between CTV-T2 5 mm and CTV T2 10, 15, or 20 mm. The sensitivity of CTV-Gd 20 mm (97%) was lower than that of CTV-T2 5 mm (98%).

Conclusions: It is necessary to use a margin of at least 2 cm around the high intensity area on T2-MRI for the initial target planning of GBM, and 5 mm around the high intensity area on T2-MRI for the recurrent target planning of GBM in the coverage of MET-PET findings.

Masayuki MATSUO (Gifu, JAPAN), Hidekazu TANAKA, Fuminori HYODO, Kazuhiro MIWA, Jun SHINODA
09:00 - 18:00 #17687 - Clinical outcomes from stereotactic radiosurgery of recurrent glioblastoma in relation to subventricular zone invasion.
Clinical outcomes from stereotactic radiosurgery of recurrent glioblastoma in relation to subventricular zone invasion.

Purpose: The benefit of radiosurgery (SRS) in recurrent glioblastoma (GBM) remains unclear, partly due to disease heterogeneity. Subventricular zone (SVZ) invasion is a prognostic factor for primary GBM, but whether SVZ involvement is also prognostic in recurrent GBM and whether SRS is useful in this setting is unknown. Here we compared outcomes from SRS and non-SRS treatment of GBM recurrence and determined whether SVZ involvement by recurrent GBM has an impact on outcomes after salvage radiosurgery.

Methods: Consecutive patients with first recurrence who were treated with SRS were retrospectively reviewed and compared with patients not treated with SRS. Propensity score matching was used to match patients. Magnetic resonance images were reviewed according to SVZ invasion by the primary tumor and at time of recurrence. Outcomes were evaluated using univariable and multivariable analyses.

Results: The median OS was 31 months in the SRS group and 15.5 months in the non-SRS group (p=0.01). The median survival after first recurrence was 18 months in the SRS group vs. 6.5 months in the non-SRS group (p=0.02). Individuals treated with SRS without SVZ involvement had the best overall survival (OS, 33months p=0.01). The median survival after first recurrence in SRS group was shorter when recurrences were localized to the SVZ ( SVZ+ vs SVZ-, 11 months vs 23 months,p=0.01), however patients with SVZ involvement treated with SRS had better overall outcomes then SVZ-negative patients not treated with SRS (OS, 28 months vs 15 months).

Conclusions: SRS appears to be an effective salvage modality for small recurrent GBMs. Although SVZ-positive tumors have a worse prognosis, these tumors may benefit from SRS. 

Maciej HARAT (Bydgoszcz, POLAND), Sebastian DZIERZECKI, Katarzyna DYTTUS-CYBULOK, Mirosław ZABEK
09:00 - 18:00 #17797 - Fractionated radiotherapy for malignant brain tumors using mask system of Leksell Gamma Knife Icon.
Fractionated radiotherapy for malignant brain tumors using mask system of Leksell Gamma Knife Icon.

Object: Leksell Gamma Knife Icon enables us to apply new methods of immobilization using mask fixation and the option of fractionated treatment. This provides exceptional accuracy and precision of radiosurgery, making it a possibility for many more disease types and many more patients to be treated. If the tumor volume was larger than 5.0 ml, recurrence, or the location was in an eloquent area, we applied a fractionated schedule.

Methods: We retrospectively analyzed 230 patients (275 times) with malignant brain tumors who underwent fractionated radiotherapy using mask system of Gamma Knife Icon between September 25th, 2017 and December 31th, 2018 at Rakusai Shimizu Hospital. The most common disease was brain metastases (221 patients), followed by glioblastoma (3), malignant lymphoma (2), anaplastic meningioma (2) and nasopharyngeal carcinoma (2). For higher accuracy, we changed the upper limit of the HDMM system from 1.5mm to 1.0mm for malignant tumors.

Results: We selected fractionated schedules as follows; 7.0 Gy x 5Fr (5-10 ml), 4.2Gy x 10Fr (10-20ml), 3.7Gy x 10Fr (20-30ml), 3.2Gy x 10Fr (30ml-) for malignant tumors. Concerning about 221 patients with brain metastases, survival rates were 79% at 6 months and 65% at 12 months, local control rates were 83% at 6 months and 63% at 12 months, and qualitative survival rates were 93% at 6 months and 89% at 12 months after Icon treatment.

Conclusions: Although these results are limited to short periods, survival rated, local control rates and qualitative survival rated in patients unsuitable for SRS, such as those with large, recurrent, and eloquent site lesions, were within the acceptable ranges. Further examination is needed for comparison with staged Gamma Knife radiotherapy, Cyber-Knife and Novalis radiotherapies

Takuya KAWABE (Kyoto, JAPAN), Manabu SATO
09:00 - 18:00 #17686 - Infiltration of glioma based on hybrid PET/MRI using 18F-FET for stereotacic radiotherapy.
Infiltration of glioma based on hybrid PET/MRI using 18F-FET for stereotacic radiotherapy.

Introduction: 

Extent of glioma infiltration using MRI imaging in not well defined and is a major factor limiting efficacy of stereotactic radiotherapy (SRT). Nevertheless in many studies results of SRT in time of recurrence was encouraging.  Up to date there is a lack of data regarding exact threshold in PET/MRI imaging, sufficient for accurate differential diagnosis between non-tumoral and tumoral changes in areas without contrast enhancement (CE) in T1-CE sequence. The aim of the study was to find the threshold between tumor infiltration and non tumoral brain tissue to improve the precison of SRT in dual-time point FET-PET/MR.

Our hypothesis was that by improving understanding of precise target definition, the role of SRT in gliomas may be redefined.

 

Methods and Results:

 

21 target points from tumor border were biopsied using hybrid PET/MRI in dual-time point aquisition (early and late examination after 18F-FET injection).  SUV values in voxels related to target points, ROI surrounding biopsy site and in contralateral brain were defined. In 7 cases non tumoral tissue, in 5 cases glioma WHO II , in 6 cases  WHO III and in 3 WHOIV tumors were diagnosed. Increased FET uptake in the area of non-CE locations on MRI correlated well with high grade gliomas localized as far as 3 cm from T1-CE foci. Selecting a target in the motor cortex based on FET kinetics defined by dual time-point PET resulted in a grade IV diagnosis after previous negative biopsies based on MRI. An additional grade III diagnosis was obtained from an area of glioma infiltration with moderate FET uptake (between 1-1.25 SUV).

Detailed correlation of all PET parameters (SUVmax, SUVmean, TBRmax, TBRmean within voxel and ROI) with histopathological  results will be presented during conference.

 

Conclusion

Stereotactic biopsy of malignant tumor infiltration not visible on T1-CE sequence based on hybrid PET/MRI imaging can be distinguished from non tumoral brain tissue and confirmed histopatologically. Finally, by using exact uptake value, measured in dual-time point aquisition of 18F-FET-PET precise target volume for stereotactic radiosurgery may be defined.

Maciej HARAT (Bydgoszcz, POLAND), Józefina RAKOWSKA, Maciej BLOK, Jacek FURTAK, Bogdan MALKOWSKI
09:00 - 18:00 #17819 - Inhomogeneous dose distribution in high-dose irradiation of brain metastases and high-grade gliomas.
Inhomogeneous dose distribution in high-dose irradiation of brain metastases and high-grade gliomas.

Objectives

This study presents a biologically-based dose distribution approach to high-dose irradiation of malignant brain tumors in order to improve treatment efficiency and safety.

Methods

Patients treated with stereotactic high-dose irradiation for large brain metastases or high-grade glioma recurrences revealing structural or metabolic heterogeneity on MRI or 11C-methionine PET/CT were included in the study. Radiation treatment was performed with Cyber Knife and linear accelerator TrueBeam STX. Delineation of tumors and their parts was performed on the basis of all available imaging studies (CT, MRI, PET). Dose distribution was optimized to achieve at least 98% coverage of the target with the prescription dose set at 70-80% isodose, high conformality, steep gradients and maximal sparing of critical structures. Distribution of higher doses inside the target took account of structural and metabolic heterogeneity. After treatment, patients underwent regular follow-up examinations (MRI or PET).

Results

The differential approach to dose distribution involves redistributing large amounts of radiation between tumor parts within prescribed general dosimetry. It has become possible thanks to cutting-edge radiation equipment, which guarantees precise dose delivery, and improvements in visualization techniques, which make visible tumor heterogeneity. Using this approach allowed us to achieve significant differences in mean doses delivered to distinct tumor parts, with higher doses targeted at solid and more metabolically active areas. At the first follow-up, the approach resulted in noticeable tumor shrinkage without MRI-detectable changes in surrounding tissues both for large metastases and glioma recurrences. Over a median follow-up period of 10 months, local control was consistently achieved for both tumor types, and no clinically relevant treatment-related complications were registered.

Conclusions

The dose redistribution approach shows promise in the targeting of large metastases and glioma recurrences with optimal effectiveness and safety.

Irina ZUBATKINA (Saint-Petersburg, RUSSIA), Pavel IVANOV, Alexandr KUZMIN, Dmitriy NIKITIN, Vladimir KRASNYUK, Darya BUTOVSKAYA, Fedor SHCHEPINOV, Yuliia MERKULOVA, Georgij ANDREEV
09:00 - 18:00 #17769 - Multisession radiosurgery re-irradiation for glioblastoma recurrence: a retrospective single center analysis.
Multisession radiosurgery re-irradiation for glioblastoma recurrence: a retrospective single center analysis.

Introduction. Despite being various treatment strategies available, recurrent multiforme glioblastomas (rGBM) are difficult to manage. Limited evidence exists to suggest the superiority of any treatment modality for rGBM. The aim of this study is to evaluate the effectiveness of multisession radiosurgery (mRS) reirradiation as salvage treatment in terms of overall survival (OS) and progression free survival (PFS).

Material and Methods. Patients previously treated with surgery and chemo-radiotherapy and re-irradiated with radiosurgery for rGBM from January 2014 to December 2016 were considered eligible. Global OS (gOS) was defined as the time between first surgery and death, OS as the time between the end of re-irradiation and death, PFS as the time between re-irradiation and disease progression. The statistical analysis was conducted using the Kaplan-Meier method.

Results. Forty-six patients were included in the analysis. Median time from primary treatment to recurrence was 14 months (range 1–79 months). Median follow-up was 4 months (range 2 days–32 months). All patients were treated with robotic radiosurgery (CyberKnife®). At the time of the analysis six of the 46 patients were alive. The median survival from initial diagnosis was 26 months (range 12–107 months). The 1-, 2-, and 3-years actuarial survival rates from diagnosis were 100, 70, and 50% respectively. Median survival following mRS was 7 months (range 1–24 months). The 1-, and 2-years actuarial survival rate following mRS were 29, and 11% respectively. The acute toxicity rate was 17%.

Conclusions. Our data suggest that mRS is a safe and effective treatment option for patients with rGBM. Further research and prospective studies are needed to better define the parameters of re-irradiation in this subset of patients.

Valentina PINZI (Milan, ITALY), Anna VIOLA, Marcello MARCHETTI, Laura FARISELLI
09:00 - 18:00 #17746 - Outcomes of patients with primary central nervous system (CNS) melanoma.
Outcomes of patients with primary central nervous system (CNS) melanoma.

Background: Primary melanocytic tumors (PMT) of the central nervous system (CNS) are exceedingly rare.  As a result, optimal management strategies are uncertain. We sought to evaluate patient outcomes in this rare tumor type.

Methods: We reviewed the records of 10 patients with PMT of the CNS treated at our institution between 2010 and 2018. 

Results: Median follow-up time was 22.1 months (range: 4.1-87.6). The median age at initial PMT diagnosis was 52.4 years (range, 27.9-83.8), with equal male: female distribution (1:1). All patients presented with neurological symptoms. Eight patients presented with solitary lesions (C-spine= 4, T-spine= 1, brain=3) whereas 2 had leptomeningeal disease (LMD). All but one PMT expressed a GNAQ mutation (n=9).  

Surgical resection was the most common initial intervention (n=9), with several patients receiving adjuvant radiation therapy (RT) (n=3) or immunotherapy (n=2) [intrathecal (IT) and intravenous (IV)]. Two patients presented with LMD and received whole brain RT (WBRT) with concurrent temozolomide (TMZ) and immunotherapy. Median survival time from initial diagnosis was 54.8 months (95% CI: 21.1- Not reached).  

Tumor control was achieved in 7 patients with the other 3 lost to follow up or rapidly progressed despite treatment, respectively. In the 7 patients in which tumor control was achieved, all relapsed (local only, n=2; LMD, n=5).  The median time to recurrence was 24.9 months (95% CI: 17.7-Not reached). Salvage therapy varied: RT alone (n=2), RT + immunotherapy (IT +/- IV) +/- TMZ (n=1), surgery + immunotherapy (IV/IT) (n=1), and immunotherapy (IV) alone (n=1). Two patients died rapidly from LMD without additional treatment. The median overall survival from the date of relapse was 19.7 months (95% CI: 19.7-Not reached).

Conclusion: Despite new advances in the treatment of cutaneous melanoma, outcomes for PMT of the CNS are poor.  Multi-institutional collaborations are needed to obtain more data for this rare CNS tumor subtype. 

Isabella Claudia GLITZA (Houston, USA), Andrew J BISHOP, Junsheng MA, Jing LI, Ian MCCUTCHEON, Claudio TATSUI, Guadagnolo ASHLEIGH
09:00 - 18:00 #17831 - Radiosurgery for Central Nervous System Lymphoma with Medical Management Failure.
Radiosurgery for Central Nervous System Lymphoma with Medical Management Failure.

Introduction: Gamma Knife Radiosurgery (GKR) for relapsed/refractory secondary CNS-lymphoma is seldom performed, while whole brain radiotherapy (WBRT) is frequently considered when medical management fails.

Objective: Evaluate GKR for secondary CNS lymphoma treated with GK-Perfexion avoiding WBRT.

Methods: A 60-year-old-man since 2016 with B-cell diffuse-lymphoma underwent treatment with R-CHOP, 6-cycles. Complete response lasted until May-2017, when he received salvage chemotherapy and autologous hematopoietic stem-cell transplant (HSCT). In October-2017, appeared diplopia and left arm paresthesias. MRI showed periventricular lesions and edema bilaterally. Stereotactic biopsy confirmed secondary CNS-lymphoma with expression of BCL-2, BCL-6 and c-MYC, triple hit. Rescue chemotherapy was repeated followed by allogenic HSCT. Complete response ensued with symptoms resolution. Generalized weakness, mood changes, attention and short-term memory impairment appeared in June-2018. Disease progression was observed in the hypothalamic and periventricular region. Patient and family refused WBRT. GKR with 13Gy at the 50% isodose was given to each lesion. Two-weeks post-GKR MRI showed remarkable response. Associated chemotherapy led to complete regression of the lesions within one month. Six-months after GKR, new diplopia occurred and MRI disclosed a midbrain tumor. He received LINAC-radiosurgery, 8 Gy in another facility. One month later he presented complete radiological response. The patient's clinical condition improved substantially after both treatments. He continues in close treatment with hematologist. To date, radiosurgery allowed avoidance of WBRT maintaining the patient with good quality of life.

Conclusion: GKR is a safe and effective alternative in the treatment of recurrent CNS-lymphomas, avoiding WBRT side effects for disease-debilitated patients. Larger series should allow better understanding of its impacts in quality of life and disease palliation. Radiosurgery dose and duration of local control must be better defined.

Rafael COSTA LIMA MAIA (São Paulo, BRAZIL), Alessandra GORGULHO, Daniel ALVES NEIVA BARBOSA, Bruno FERNANDES DE OLIVEIRA SANTOS, Crystian WILIAN CHAGAS SARAIVA, Anderson MARTINS PASSARO, Antonio DE SALLES
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P05
09:00 - 18:00

EPOSTER - 05 Liver/Pancreas
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17847 - Australian experience of stereotactic radiation therapy in early and advanced stage hepatocellular carcinoma.
Australian experience of stereotactic radiation therapy in early and advanced stage hepatocellular carcinoma.

Purpose

Intra-hepatic progression remains the predominant mode of death in hepatocellular carcinoma (HCC). Stereotactic radiotherapy (SBRT) is an emerging non-invasive locoregional therapy for early to advanced HCC. We report our early experience at an Australian tertiary liver centre.

Methods and Materials

Retrospective study of patients treated between October 2013 and June 2018. Efficacy of SBRT was determined by in-field local control (LC) with CT or MRI, utilizing Response Evaluation Criteria in Solid Tumours (RECIST). Kaplan-Meier methodology was used to determine one year LC, progression free survival (PFS) and overall survival (OS) from date of SBRT. Toxicity was assessed by CTCAE V4.

Results

Ninety-five lesions in 79 patients were treated. Median age was 65 years (range 35-88), 89% male, baseline liver function Child-Turcotte-Pugh (CTP) A (72%), CTP-B (14%), non-cirrhotic (14%). Barcelona Clinic Liver Cancer (BCLC) stage was 0/A (61%), B (9%) and C (30%), with 50% receiving prior liver-directed therapies (median 2 courses, range 1-5). Median tumour diameter was 4.8cm (range 1.5-17cm), Macrovascular invasion was present in 18 (25%), IVC invasion in 5 (7%). Median follow-up was 8 months (range, 1-54). One year LC for BCLC 0/A and B/C cohorts was 95% and 73% with median covering isodoses of 40Gy and 35Gy in 5 fractions respectively. One year LC was 100% if both CTP-A and BCLC 0/A. Local recurrence type was in-field (n=2) and edge-of-field (n=3). Intra-hepatic relapse occurred in 20 (28%) and extrahepatic relapse in 11 (15%). One year PFS and OS was 74% and 89% for BCLC 0/A, 34% and 52% for BCLC B/C disease. Two of 48 patients who were progression free had an increase in CTP score >1, both with intercurrent illness (pneumonia, endocarditis). There were no other non-liver, grade ≥3 gastrointestinal toxicity events. The commonest grade 2 clinical toxicities included fatigue (18%) and pain (3%).

Conclusion

SBRT provides high rates of local control in early to advanced stage HCC and is well tolerated, even in a heavily pre-treated cohort. Out of field relapse is common in advanced stage HCC supporting a rationale to investigate SBRT in combination with other locoregional and emerging systemic therapies.

David PRYOR, David PRYOR (Brisbane, AUSTRALIA), Howard LIU, Dominique LEE, Peter HODGKINSON, Katherine STUART
09:00 - 18:00 #17786 - Liver stereotactic radiotherapy in heavily pre-treated elderly patients – single institution retrospective experience.
Liver stereotactic radiotherapy in heavily pre-treated elderly patients – single institution retrospective experience.

Background: Liver SABR is increasingly being integrated into multimodality treatment pathways due to advances in treatment delivery, image guidance, and promising outcome data. Tolerability and toxicity, especially among pre-treated elderly patients with multiple comorbidities, is still a matter of concern in clinical practice.

Methods: We undertook a single institution retrospective analysis of patients treated with linac-based liver SABR between January 2016 and January 2019 at Guy’s Cancer Centre, London.

Results: There were 30 tumours from 27 patients of which 13 were Colorectal metastases (CRCm), 11 Hepatocellular carcinoma (HCC) and 3 Cholangiocarcinoma (CHC). Median age was 72 (36-91); 19 patients were ≥70 years old; median ECOG performance status was 1 (range 0-2). Many patients were heavily pre-treated and not suitable for other therapies due to comorbidities or lack of treatment options. All HCC patients were Child-Pugh A and 63% of these were non-viral aetiology; 2 patients were treated as a bridge to transplant. Median tumour size was 4 cm (1.3-9.5). Median prescription dose was 50Gy (40-60) delivered in 3-10 fractions, with median GTV and liver volumes of 67.5cc (27-188) and 1496.1cc (1060-2651) respectively. Median dose to 700cc Liver-GTV was 10.5Gy (7-27.8). 9 treatments (36%) were performed in end expiratory breath hold (EEBH). Six weeks post-radiotherapy, fatigue G1 was the only treatment-related toxicity reported by 31% of patients; 27% were asymptomatic and 1 developed a duodenal ulcer. Median liver function test results were bilirubin 11 umol/L(5-32), AST/ALT 37 IU/L (16-136), albumin 38.5 g/L (30-45) and ALP 162 IU/L (60-649). At 6 months, 3 patients died from out-of-field progression (2CRCm; 1HCC); 85% of patients reported no toxicities. One death from radiation-induced hepatic decompensation and extrahepatic disease progression was reported after 8 months. 1-year actuarial survival was 71%; 6 patients remained asymptomatic. There was an asymptomatic duodenal perforation managed conservatively and one SABR-induced liver dysfunction with no active disease that recovered completely.

Conclusion: Liver SABR is safe, effective, and well tolerated in heavily pre-treated elderly patients with multiple comorbidities.

Pollyanna D AVILA LEITE (London, UK), Asad QURESHI, Kasia OWCZARCZYK, Benjamin TAYLOR, Clare HARTILL, James BARBER, Mark MCGOVERN, Vicky GOH, Andrew GAYA
09:00 - 18:00 #17852 - Phase II trial of high dose stereotactic body radiation therapy for abdomen and pelvis lymph node metastases.
Phase II trial of high dose stereotactic body radiation therapy for abdomen and pelvis lymph node metastases.

Background: Stereotactic body radiotherapy (SBRT) is nowadays considered an effective approach for the management of oligometastatic patients. We analyzed clinical results of oligometastatic patients treated with high dose SBRT for lymph node metastases in abdomen and pelvis.

Materials and Methods: This is a prospective, phase II study. Primary end-point was the assessment of acute and late toxicity; secondary end-points were local control (LC), progression free survival (PFS) and overall survival (OS) The schedule of SBRT was 48 Gy delivered in 4 fractions of 12 Gy each. Inclusion criteria were: Histologically-proven carcinoma of gastro-intestinal, genito-urinary of gynecological primary districts, maximum 3 lymph node sites of disease, maximum diameter ≤ 5 cm

Results: From 2015 to May 2018, 43 patients with 54 lymph nodes were enrolled. Genito-urinary (69.7%) and in particular prostate adenocarcinoma (61.1%) was the most common site of primary tumour, followed by gastro-intestinal (25.6%) and gynecological (4.6%). One single lymph node was treated 34 patients, while 2 and 3 lymph nodes in 7 and 2 patients, respectively. With a median follow-up of 16.7 months, only 3 patients reported grade 1 acute toxicity, in the form of pain, dysuria and fatigue. In the late setting, chronic pain was observed in 1 patient. In-field progression was observed in 5 patients with a 1- and 2- years rate of 96.6% and 80.6%.  Systemic therapy during SBRT was associated with a worse LC (HR 10.3, p=0.012). Rates of PFS at 1- and 2-years were 82.8%% and 57.1%. Median PFS was 26.1 months. One and 2-years were OS of 100% and 95.6%.

Conclusion: Treatment of lymph node metastases with high dose SBRT can be considered a safe option in a multidisciplinary approach, with high rates of local control. One year median delay of new system therapy has been demonstrated in this phase II trial. 

Ciro FRANZESE (Milano, ITALY), Davide FRANCESCHINI, Tiziana COMITO, Angelo TOZZI, Fiorenza DE ROSE, Pierina NAVARRIA, Giuseppe Roberto D'AGOSTINO, Giacomo REGGIORI, Stefano TOMATIS, Marta SCORSETTI
09:00 - 18:00 #17853 - Role of Stereotactic body radiation therapy in the management of oligometastatic pancreatic cancer: single institution experience.
Role of Stereotactic body radiation therapy in the management of oligometastatic pancreatic cancer: single institution experience.

Introduction: Despite recent advancement in systemic and local treatments, prognosis of patients with pancreatic cancer (PC) still remains poor, with 5 year survival less than 10%. According to literature, a percentage of cancer patients will develop a limited number of metastases, defined as oligometastatic disease. Aim of our study was to evaluate efficacy of Stereotactic body radiation therapy (SBRT) in selected oligometastatic PC.

 Materials and methods: We included patients with a with a maximum of 5 metastases in up to 2 sites. Tumor response was graded according to EORTC-RECIST criteria. Endpoints  were local control (LC), progression free survival (PFS) and overall survival (OS).

 Results: From 2013 to 2017, a total of 41 patients was treated on 64 metastases. Seven (17.1%) patients were naive to systemic therapy at time of SBRT and 25 (61%) patients were treated on one single lesion. Most common sites of disease were lung (29.3%) and liver (56.1%). Median Biologic effective dose (BED) was 105.6 Gy (57.6 – 262.5). Rates of LC  at 1 and 2 years were 88.9% and 73.9%.  Median LC was 39.9 months. Rates of PFS at 1 and 2 years were 21.9% and 10.9%. Median PFS was  5.4 months. At multivariable analysis sex (HR  4.59; p=0.001), time to metastases (HR 0.96; p=0.031) and extra-target disease (HR 7.36; p=0.001) were significant for PFS. Rates of OS at 1 and 2 years were 79.9% and 46.7%. Median OS was 23 months.  At univariate analysis time to metastases (HR 0.95; p=0.036), and BED (HR 1.00; p=0.017) were significant for OS.     

 Conclusion: Our study shows that SBRT on oligometastases from pancreatic cancer is a feasible and effective approach in terms of local disease control. Prospective trials are necessary to improve patient’s selection and to better define the integration of local treatment with more effective systemic therapy.  

Ciro FRANZESE (Milano, ITALY), Tiziana COMITO, Davide FRANCESCHINI, Ilaria RENNA, Angelo TOZZI, Fiorenza DE ROSE, Pierina NAVARRIA, Giacomo REGGIORI, Stefano TOMATIS, Marta SCORSETTI
09:00 - 18:00 #17601 - Stereotactic body radiation therapy as management of functional neuroendocrine neoplasms.
Stereotactic body radiation therapy as management of functional neuroendocrine neoplasms.

Neuroendocrine neoplasms (NEN) are heterogeneous malignancies that commonly arise in the lungs, GI tract and pancreas. One unique characteristic of these tumors can be the dysregulated secretion of hormones.  Due to unique indolent biology patients can be managed for many years with prolonged survival; the challenge in managing this patient population is to obtain both tumor and hormonal control. 

Patients with NEN require multidisciplinary assessment and care. For localized disease, surgical resection may be performed with curative intent.  Even in the scenario of metastatic disease, aggressive surgical debulking may improve quality of life by decreasing tumor burden and lessening hormonal production. Non-surgical options for metastatic disease include liver-directed therapy such as ablation or liver embolization, as well as systemic therapy, including somatostatin analogues (SSA), peptide receptor radionuclide therapy (PRRT), targeted agents or traditional cytotoxic chemotherapy.

External beam radiation has been sparingly used for NEN, due to modest responses seen with conventionally delivered treatment. The development of stereotactic body radiation therapy (SBRT) has been made possible by technical advances within the radiation planning and delivery process. SBRT is characterized by high ablative doses delivered over a few treatments and is increasingly utilized technique for both primary and metastatic solid tumors. Despite the rapid uptake of SBRT within other cancers, there are limited data evaluating its impact within NENs, and specifically on hormonal control in this patient population. We submit a series of 4 patients (2 insulinoma, 1 glucagonoma and 1 bronchial) in which SBRT has been utilized as part of multidisciplinary management of primary or metastatic neuroendocrine disease. Each patient was treated with SBRT to either the primary/dominalnt metastatic site of disease or the end organ of hormonal release. No significant toxicity was noted during or after treatment. Each patient had biochemical, clinical and radiographic response to therapy. These cases represent proof of concept that SBRT is an effective therapeutic strategy for functional neuroendocrine neoplasms.

Sten MYREHAUG (Toronto, CANADA), Julie HALLET, William CHU, Elaine YONG, Calvin LAW, Angela ASSAL, Alexander LOUIE, Simron SINGH
09:00 - 18:00 #17616 - Stereotactic body radiation therapy for oligometastatic gastric cancer.
Stereotactic body radiation therapy for oligometastatic gastric cancer.

Purpose : To evaluate the efficacy of stereotactic body radiotherapy (SBRT) for oligometastatic gastric cancer

Methods and materials : Between January 2005 and November 2017, 30 patients with 35 oligometastatic lesions from gastric cancer were treated with SBRT. All patients had metastatic lesions of 3 or less with controlled primary tumor. We divided the 33 lesions into three groups : Group A (n=18), abdominal lymph nodes; Group B (n=11), liver; Group C (n=6), others. The median follow-up period was 34 months (range; 3-85). The median tumor volume was 5.8 ml (range, 0.4-204 ml). The prescribed dose ranged from 30 to 60 Gy in 3-5 fractions. 

Results : Involved field failure occurred in 5 lesions (14.3%), regional recurrence occurred in 14 lesions (40.0%) and the distant metastases occurred in 9 lesions (25.7%). The 5-year overall survival rate of group A, B and C were 38.8%, 56.0% and 20.0%, respectively. The 5-year involved field control rate of group A, B and C were 92.3%, 87.59% and 40.0%, respectively. The 5-year progression-free survival rate of group A, B, and C were 33.3%, 56.0%, and 0.0%, respectively. Only two patients experienced grade 2 toxicity, gastrointestinal bleeding in one and radiation pneumonitis in the other. There was no grade 3 or higher acute or late toxicity.

Conclusion : The survival of patients with oligometastases of gastric cancer differed according to the site of recurrence. SBRT could be a safe and effective treatment option to treat oligometastatic lesions from gastric cancer, especially for liver metastases. The selected abdominal lymph node also could be treated effectively with SBRT.

Won Il JANG (SEOUL, KOREA), Mi-Sook KIM, Chul Koo CHO, Kwang Mo YANG, Hyung Jun YOO, Eun Kyung PAIK, Eunji KIM, Hee Kyung JEONG, Dong Han LEE, Kyubo KIM
09:00 - 18:00 #17562 - Stereotactic body radiotherapy as a part of combine treatment or single modality for patients with oligometastatic liver disease: own experience.
Stereotactic body radiotherapy as a part of combine treatment or single modality for patients with oligometastatic liver disease: own experience.

Purpose: To determine the importance of maintaining treated metastases control for progression-free survival in patients with oligometastatic liver disease. To conduct if stereotactic body radiotherapy might be more effective alone or combined with systemic therapy.

Methods and Materials: Since 2012 until 2018, 45 patients with 69 lesions were treated. There were 35 patients who had been treated with chemotherapy before stereotactic body radiotherapy. Average lesion volume was 35,2 cc. Histological types were represented mostly by colorectal cancer(72,5%). Respiratory tracking motion systems were used in all cases, with fiducial tracking motion system for patients treated with Cyberknife, and daily ConeBeamCT for patients treated with Truebeam.

Results: Median follow-up was 9 months. Treated metastases control was achieved in all cases with median of 6 months, and it had strong correlation with progression-free survival (p<0,05; 0,73). Patients who received stereotactic body radiotherapy after a few courses of chemotherapy with partial response had longer progression-free survival than patients with stabilization or progression after chemotherapy(median of 25 mo feat 4 mo; p=0,005) or without chemotherapy at all(median of 3,5 mo; p=0,005). The same pattern persisted for treated metastases control. There was no significant correlation between BED10 or target volume and TMC (0,15 and 0,17; p<0,05).

Conclusion: Achievement of local control is an important part of treatment for patients with oligometastatic disease. According to literature, pre-SBRT chemotherapy was related to favorable overall survival, but also the response of chemotherapy can be seen as a prognostic factor of progression-free survival and treated metastases control for patients with oligometastatic liver disease. A significant impact of BED10 on local control couldn’t be seen, possibly because of too narrow dosage range.

Natalia MARTYNOVA (Saint-Petersburg, RUSSIA), Nikolay VOROBYOV, Darya KUPLEVATSKAYA, Alina SMIRNOVA, Julia GUTSALO, Aleksey MIKHAYLOV, Denis ANTIPIN, Georgy ANDREEV, Anton KUBASOV
09:00 - 18:00 #17649 - Stereotactic body radiotherapy for unresectable pancreatic cancer protocol and first implementation.
Stereotactic body radiotherapy for unresectable pancreatic cancer protocol and first implementation.

Introduction

Unresectable pancreatic cancer remains a challenging disease to treat. The role of radiation therapy in the management of such cases is still controversial. The aim of this work is to describe the protocol adopted in Hygeia Hospital, Athens, Greece for the implementation of SBRT to patients with unresectable pancreatic cancer.

Materials and Methods

The inclusion criteria are: age≥18years, histologically proven unresectable primary adenocarcinoma, neo-adjuvant chemotherapy, lesion diameter<5cm, Karnofsky Performance score³70. Patients are immobilized in supine position using Deep Inspiration Breath Hold technique. Patients are given a barium meal 15min prior to imaging for visualization of the stomach and duodenum. Clinical Target Volume (CTV) is delineated on the arterial phase of the planning CT scan (1mm slice thickness) using registered MR images. Additional margins of 5mm in the left-right direction, 5mm in the anterior-posterior direction and 10mm in the cranial-caudal direction are used to form the Planning Target Volume (PTV). Dose prescription is 40Gy in 5 fractions delivered over a two weeks period. Patient plans are created with Elekta Monaco TPS and are treated on an Elekta VersaHD Linac using a 10 MV Flattening Filter Free (FFF) beam. Patients should fast 3hrs prior to treatment and be given a barium meal 15min before being treated. Accurate patient positioning is verified with CBCT image guidance.Five male patients (median age 55yrs) were treated with the SBRT departmental protocol for unresectable pancreatic cancer.

 

Results

All patients treated showed well tolerated gastrointestinal grade I-II toxicity, confirming that the departmental SBRT protocol is well within international guidelines and could be used for treatment of patients with unresectable pancreatic cancer.

 

Conclusion

Patients with locally advanced, inoperable pancreatic cancer can be safely treated with SBRT, in short duration fractionation scheme with minimum disruption of chemotherapy treatment, resulting in less toxicity and better quality of life.

Georgios KRITSELIS (ATHENS, GREECE), Chryssa PARASKEVOPOULOU, Nikolaos GIAKOUMAKIS , Efi KOUTSOUVELI , Pantelis KARAISKOS, Georgios KOLLIAS
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P06
09:00 - 18:00

EPOSTER - 06 Lung
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17629 - Comparing phase- and amplitude-gated volumetric modulated arc therapy for stereotactic body radiation therapy using 3D printed lung phantom.
Comparing phase- and amplitude-gated volumetric modulated arc therapy for stereotactic body radiation therapy using 3D printed lung phantom.

Purpose: To compare the dosimetric impact and treatment delivery efficacy of phase-gated volumetric modulated arc therapy (VMAT) versus amplitude-gated VMAT for stereotactic body radiation therapy (SBRT) for lung cancer by using realistic 3D-printed phantoms

Methods: Four patient-specific moving lung phantoms that closely simulate the heterogeneity of lung tissue and breathing patterns were fabricated with four planning computed tomography (CT) images for lung SBRT cases. The phantoms were designed to be bisected for the measurement of 2D dose distributions by using EBT3 dosimetry film. The dosimetric accuracy of treatment under respiratory motion was analyzed with the gamma index (2%/1 mm) between the plan dose and film dose measured under phase- and amplitude-gated VMAT. For the validation of the direct usage of the real-time position management (RPM) data for respiratory motion, the relationship between the RPM signal and the diaphragm position was measured by 4D CT. By using data recorded during the beam delivery of both phase- and amplitude-gated VMAT, the total time intervals were compared for each treatment mode.

Results: Film dosimetry showed a 5.2 ± 4.2% difference of gamma passing rate (2%/1 mm) on average between the phase- versus amplitude-gated VMAT (77.7% [72.7%–85.9%] for the phase mode and 82.9% [81.4%–86.2%] for the amplitude mode). For delivery efficiency, frequent interruptions were observed during the phase-gated VMAT, which stopped the beam delivery and required a certain amount of time before resuming the beam. This abnormality in phase-gated VMAT caused a prolonged treatment delivery time of 366 s compared with 183 s for amplitude-gated VMAT.

Conclusions: Considering the dosimetric accuracy and delivery efficacy between the gating methods, amplitude mode is superior to phase mode for gated VMAT treatment.

Kyoungjun YOON (Korea, KOREA), Minsik LEE, Byungchul CHO, Su Ssan KIM, Si Yeol SONG, Eun Kyung CHOI, Seungdo AHN, Sang-Wook LEE, Jungwon KWAK
09:00 - 18:00 #17664 - Estimating the probability of local control, depending on fractionation for tongue cancer.
Estimating the probability of local control, depending on fractionation for tongue cancer.

Malignant neoplasms of the head and neck are characterized by a high proliferation rate during radiation treatment. Modern equipment for radiotherapy (RT) allows to increase the dose per fraction (i.e., implement hypofractionation) without complications of organ at risk and reduce the total time of the entire RT course. Hypofractionated RT for head and neck cancer could increase the treatment effectiveness in terms of tumor control probability (TCP).

The aim of the work is to investigate the dependence of the TCP for head and neck tumors on the total course dose and dose per fraction values, and to analyze hypofractionated VMAT dosimetric plans from the radiobiological point of view in order to maximize TCP value. This investigation was carried out using data of the patients with tongue cancer.

The data of four patients with tongue cancer of second and third stages (T2N0M0-T3N2M0) was used during this investigation. All VMAT treatment plans were created using Elekta MONACO planning system and delivered at Elekta Synergy linac.  Simultaneously integrated boost (SIB-VMAT) technic was used.
TCP values were calculated using at-home developed code in Wolfram Mathematica based on Niemierko model using the parameters of  and  for head neck tumors (Maciejewski and et al, 1989). Since head and neck tumors are characterized by high proliferation rate with a doubling time of 3 days, starting, according to different estimates after 14-30 days of treatment,  were taken for different treatment durations (5, 6, or 7 weeks) .

TCP calculation results show that increase of treatment duration for the stages (T2N0M0-T3N2M0) significantly reduces TCP. Thus, for RT with standard fractionation of 35 fractions and 2 Gy per fraction, the TCP values for the stages T2N0M0-T3N1-2Mis equal to 77%, and for T3N3M0 – 68%. In order to obtain TCP values more than 95% for the second and third stages using standard fractionation of 2 Gy / fraction, one needs to increase total dose to 78 Gy, resulting in TCP values more than 95%. A more rational alternative is the use of hypofractionation, i.e. increase fractional dose. Indeed, the dose of 70 Gy delivered over 30 fractions allows to obtain TCP values for the stages T2N1-3M0-T3N1-2M0 equal to 98.7%, and for the stage T3N3M0 – 98.0%. Reduction of the duration of treatment to 25 fractions will allow obtaining TCP values more than 99.8%.

Sukhikh EVGENYA (Tomsk, RUSSIA), Sukhikh LEONID
09:00 - 18:00 #16999 - First Report of Pulmonary Large Cell Neuroendocrine Carcinoma Treated with Stereotactic Body Radiation Therapy.
First Report of Pulmonary Large Cell Neuroendocrine Carcinoma Treated with Stereotactic Body Radiation Therapy.

INTRODUCTION: Pulmonary large-cell neuroendocrine carcinoma (LCNEC) is a very rare disease, comprising approximately 3% of lung cancers.  Even for Stage I disease, recurrence after resection is common, with a poor five-year overall survival. We present the first report of stereotactic body radiotherapy (SBRT) for pulmonary LCNEC.

METHODS: A 54-year-old woman with a left upper lobe pulmonary nodule underwent a wedge resection with thoracoscopic mediastinal lymph node dissection, revealing a 2.3 cm pT1b N0 LCNEC. Approximately one year later, surveillance imaging demonstrated a new left upper lobe PET-avid nodule, resulting in completion left upper lobectomy revealing LCNEC, with 0/6 involved lymph nodes and negative staging studies. The patient subsequently chose surveillance over adjuvant chemotherapy; unfortunately 23 months later imaging revealed an enlarging 0.7 cm nodule adjacent to the previous resection site, despite the patient remaining in good health (KPS=90).  Subsequent restaging demonstrated no evidence of metastatic disease.  Due to the morbidity of a third operation in this region, and based on the safety of SBRT for Stage I non small-cell lung cancer, the consensus decision from our thoracic oncology team was to proceed with SBRT as preferred management for presumptive second recurrence of LCNEC. The patient shortly thereafter underwent SBRT (50 Gy in 10 Gy/fraction) to this new nodule, 41 months following initial LCNEC diagnosis.

RESULTS: Four months following SBRT, the patient remains in excellent clinical condition (KPS 90), with no evidence of disease spread on surveillance studies.  The nodule itself demonstrated no evidence of growth following SBRT.

CONCLUSIONS: This first report of SBRT for pulmonary LCNEC demonstrates that SBRT is a feasible modality for this rare disease.  A multidisciplinary thoracic oncology approach involving medical oncology, thoracic surgery, radiation oncology and pulmonology is strongly recommended to ensure proper patient selection for receipt of SBRT.

Shearwood MCCLELLAND III (Indianapolis, USA), Gregory DURM, Thomas J BIRDAS, Paul M MUSTO, Tim LAUTENSCHLAEGER
09:00 - 18:00 #17716 - ITV calculation for lung SBRT treatment with CBCT during free breathing cycles. Case Report.
ITV calculation for lung SBRT treatment with CBCT during free breathing cycles. Case Report.

SBRT refers to the precise irradiation of an image define extracranial target using a small number of high dose fractions.  SBRT it is a useful treatment option for lung cancer in carefully selected patients.

The variation in clinical target volume (CTV) position and size due to respiratory motion is generally accounted by adding an internal margin to the CTV, resulting in the internal target volume (ITV).

Cone beam (CBCT) is increasingly being used for localization of lung tumours. CBCT scans can have an acquisition time 60s or more, an therefore have the advantage of capturing the average tumour position over 15 or more breathing cycles, which may correspond well to the planning internal target volume as obtained from 4D CT.

In the absence of 4DCT as a simulation image set, this work aims to show the possibility of calculating the ITV of lung lesions greater than 2 cm using multiple CBCT as complementary images to those of free breathing tomography simulation using a respiration correlated approach (flux med).


We analysed the inter-observer differences in blurring delimitation of the lesion with the objective of validate the use of CBCT as an image set to estimate ITV of lung lesions during free breathing cycle as well as the reproducibility of this target verification using CBCT after exactrac positioning using surrogate isocenter in proximal vertebral body in Varian Trilogy LINAC with Exactrac and 6D couch technology. 

Ruben Oscar FARIAS, Florencia MAURI, Leon ALDROVANDI, Augusto ALVA, Maria Liliana MAIRAL, Mabel Edith SARDI, Federico Javier DIAZ, Mara Lia SCARABINO (Buenos Aires, ARGENTINA)
09:00 - 18:00 #17658 - Lung cancer stereotactic radiotherapy at genesiscare victoria australia: 3D conformal radiotherapy vs dynamic conformal arc therapy.
Lung cancer stereotactic radiotherapy at genesiscare victoria australia: 3D conformal radiotherapy vs dynamic conformal arc therapy.

This retrospective study aims to show a dosimetric comparison between three-dimensional conformal radiotherapy (3DCRT) and dynamic conformal radiotherapy (DCAT) for Lung cancer patients being treated with stereotactic body radiotherapy (SBRT). The study compares 3DCRT and DCAT plans for twenty clinical lung cancer patients that were treated at GenesisCare Victoria in 2018. The aim of this planning study is to help planners identify early in the planning process which technique will give optimal results for the patient. Each of the twenty patients met an eligibility criteria and were all planned for TrueBeam™ machine delivery using Pinnacle3 ™ radiation therapy treatment planning system.

 

Following guidelines outlined in RTOG 0915 for Planning treatment volume (PTV) reporting and Organs at Risk (OAR) tolerances, the tumour coverage was maintained between both techniques (D95%>100%, minor variation D99%>90%). Preliminary findings indicate higher R50 (50% isodose) and D2 (Max dose at 2cm from PTV) values in the 3DCRT plans.  Full cohort of patient’s results will be outlined at the congress. Ultimately both techniques are viable and safe treatment options for delivery of SBRT, however factors such as of lesion position, arm placement and OAR proximity need to be considered when deciding between 3DCRT and DCAT for optimal planning outcomes.

Stephanie BARNAO (Melbourne, AUSTRALIA), Michael NG, Tam NGUYEN
09:00 - 18:00 #17878 - Preliminar results of cyberknife stereotactic radiotherapy for oligometastatic non small cell lung cancer.
Preliminar results of cyberknife stereotactic radiotherapy for oligometastatic non small cell lung cancer.

Aims: Stereotactic radiotherapy (SRT) is a therapeutic possibility for selected oligo-metastatic/oligo-progressive (OM/OP) non-small cell lung cancer (NSCLC), that  is one of the tumour most frequently treated with SRT. We retrospective analyzed clinical outcomes and treatment related toxicities of a cohort of  patients (pts) treated with Cyberknife - SRT for OM/OP NSCLC at Cyberknife Unit, Centro Diagnostico Italiano (CDI), Milan, italy.Patients and methods: We retrospective analyzed 39 OM/OP NSCLC pts treated in our Center  from January 2016 to January 2017. OM/OP disease was defined as one to five metastatic lesions. 30 pts (77%) had adenocarcinoma histology (6 and 2 pts with EGFR and ALK mutation respectively). The median age at the treatment was 69 years, and most of the pts with a high performance status (74% with a Karnofsky Index  90 or more). Most of patients have been already treated (with 1 and 2 systemic therapy lines, surgery or radiotherapy) for metastatic disease before Cyberknife. 16 pts continued systemic therapy during SRT. At the time of radiotherapy, 72% of pts were oligometastatic, while 28 % had oligoprogressive disease. Of the 55 treated lesions, 29 were brain metastasis (53%), 13 lung metastases (24%), 4 bone metastases (7%) and respectively 7 (13 %) 1 (2%) and 2 (4%) lesions were lymph nodes, adrenal and other sites.Results:  After a median follow-up of 17 months, overall survival was 94.65% (range 87.43 -100) and 82.43% (range 67.77 – 97.09) at 1 and 2 years, respectively; one year local progression free survival (LPFS) and progression free survival (PFS) were 91.47% (82.17-100) and 38.46% (23.19-53.75) respectively. The pattern of progression was analyzed for 73 pts showing no progression for 27 pts (37%), oligo-progression in 30 pts (41%) and poli-progressive disease in 16 cases (22%). The majority of pts did not reported any acute toxicities (only one patient has experienced a G2 neurotoxicity). Regarding late toxicity 3 pts reported G2 neurotoxicity while 1 patient died for radionecrosis after a treatment for brain metastases. Conclusions: in our preliminar data SRT-Cyberknife appears to be safe and effective in OM/OP NSCLC, with promising results according to the literature.

Isa BOSSI ZANETTI (Milano, ITALY), Livia Corinna BIANCHI, Achille BERGANTIN, Anna Stefania MARTINOTTI, Irene REDAELLI, Paolo BONFANTI, Chiara SPADAVECCHIA, Giancarlo BELTRAMO
09:00 - 18:00 #17561 - Primary and metastatic lung tumors treated with stereotactic body radiation therapy: own experience.
Primary and metastatic lung tumors treated with stereotactic body radiation therapy: own experience.

Purpose: Assessing stereotactic body radiotherapy efficiency and toxicity for primary lung cancer and lung metastases.
Methods and Materials: In a period from December 2011 to February 2017, 71 patients with primary and metastatic lung tumors were treated. Stereotactic body radiotherapy was applied to 103 tumors: 33 primary tumors, 70 metastases of different tumor sites. Two linear accelerators with different respiratory motion tracking systems were used: CyberKnife with Synchrony respiratory motion tracking system and TrueBeam STx with Gating.
Results: Clinical observation group include 52 patients with 81 lung tumors. Average tumor volume was 44.7 cc (0.2-496.5 cc). Observation median was 7 months. Local control was achieved in all cases, median of local control was 6 months. For 19(23.5%) tumors complete response was achieved, median was 5 months. There was a local relapse in 17(21%) cases, 15 of which were squamous cell relapse. There was a negative linear dependence of local relapse probability from BED10 for squamous cell tumors. Disease progression was observed among 29 patients, 93% of them had a local control preserved during the whole observation period. Early toxicity was grade 1-2 for most patients; 5 patients with large tumor volume (more than 300 cc) had grade 3 early toxicity. None of the patients had grade 4 early toxicity. Late toxicity did not exceed grade 2 for all the patients.
Conclusion: Stereotactic body radiotherapy appears to be safe and effective treatment option for patients with lung lesions, including huge and central tumors. It allows to use higher radiation doses even in palliative care.  Potentially, higher radiation doses are needed to achieve better local control for squamous cell tumors. 

Natalia MARTYNOVA (Saint-Petersburg, RUSSIA), Nikolay VOROBYOV, Aleksey MIKHAYLOV, Julia GUTSALO, Georgy ANDREEV, Anton KUBASOV
09:00 - 18:00 #17757 - SBRT: 1, 3 or 5 fractions in the treatment of lung tumors in elderly patients.
SBRT: 1, 3 or 5 fractions in the treatment of lung tumors in elderly patients.

BACKGROUND/PURPOSE/OBJECTIVES

The aim of this study is to describe the impact of fractionation scheme on results with SBRT for lung tumors in elderly patients.

MATERIALS/METHODS

Our institutional lung SBRT experience for patients aged 75 years or older, extracting details of patient factors, treatment specifics, toxicity and clinical outcomes.

Local control and survival rates were calculated and compared between subsets of patients.     All events were calculated from the end of radiation therapy.  Toxicity and radiologic response were assessed using standardized criteria. Cause-specific survival and overall survival were calculated using the Kaplan-Meier method.  Outcomes were compared for those with single 30 Gy fraction and other schemas. 

 

RESULTS

Between 2002 and 2017, 104 patients had 121 SBRT procedures; 67 were for primary lung tumors (T1-2N0M0) and 44 oligometastases. Median patient age was 79.6 years (75-88).  All cases had ECOG PS 0-1.

Treatments schema:  30 Gy single fraction (n=12), 45-48 Gy in 3 fractions (n=81)  and 50 Gy in 5 fractions- (n=26)

In a comparison of single and multiple fractions cohort, patient and tumor characteristics were balanced and median follow-up was 16 months (2-70).

For the 30 Gy and other schedules rates of 1-year local control, overall survival and cancer specific survival were 100% vs 98 %; 84 % vs 78 % and 92 % vs 90 %, respectively (p differences were not significant).

Median ITV was 11.6 cm3 (0.9-143) BED>100Gy. Transient grade 1-2 acute toxicities in 11 %.  No grade > 3 acute or any chronic toxicities.

OS was significantly influenced by pretreatment performance status, primary tumor histology and ptv size in metastases.  For LC pretreatment performance status was the only prognostic factor.  No factor significantly influenced toxicity.

 

CONCLUSIONS

Excellent OS and LC is achievable in elderly patients.  In our cohort there were no differences in results comparing single vs multifraction lung SBRT.

Luis LARREA (Valencia, SPAIN), Enrique LOPEZ-MUNOZ, Paola ANTONINI, Veronica GONZALEZ, Jose BEA-GILABERT, Maria BANOS-CAPILLA
09:00 - 18:00 #17714 - Timing of PET for diagnosis of local recurrence of NSCLC after SBRT using SULmax.
Timing of PET for diagnosis of local recurrence of NSCLC after SBRT using SULmax.

Maximum standardised uptake value (SUVmax) is measured with 18F-Fludeoxyglucose (FDG) positron emission tomography (PET) and has previously been investigated as a marker for local recurrence of non-small cell lung cancer (NSCLC) with mixed results, possibly due to the acute radiation inflammatory response in the first 3-9 months. The authors assessed the accuracy of semi-quantitative PET measurements to detect local recurrence at different time points after SBRT.

Method

A retrospective review was performed of patients with stage1 NSCLC treated with stereotactic body radiation (SBRT) who underwent follow-up PET scan/s at a single centre. Maximum standardised uptake value normalised for lean body mass (SULmax) was calculated for the primary tumour including surrounding CT changes. Outcomes of local recurrence, locoregional recurrence and distant metastasis were diagnosed based on histopathology where available, and clinical follow-up.

Results

52 lesions underwent a total of 107 follow-up PET scans after treatment with SBRT. Prescribed doses were between 48-60Gy in 4-8fractions.The median time to first PET scan was 9.3 months, and the median follow-up period was 22.4months (range 6.5-54 months). 

Local recurrence was diagnosed in 10 patients (19%), of which 5 were histopathology confirmed, at a median period of 16 months. Locoregional recurrence and distant metastasis were diagnosed in 9 and 11 patients respectively. The median SULmax was significantly higher for local recurrences compared to non-recurrences (5.97 vs 2.27) and a threshold of SULmax>5 yielded a sensitivity of 90% and specificity of 88%.

33 PET scans were performed within 9 months of SBRT, which found that SULmax was not specific with 3 false positives.  Beyond 9 months, SULmax>5 has a sensitivity of 90% and specificity of 94%.

Conclusion

Beyond 9 months after SBRT, SULmax can reliably identify local recurrence.

Further studies are required to investigate the utility of SULmax earlier than 9 months after SABR.

Daren TAN (Perth, AUSTRALIA), Suki GILL, Nelson LOH
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P07
09:00 - 18:00

EPOSTER - 07 Meningioma
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17628 - Dosimetric comparison between CyberKnife and GammaKnife hypofractionated radiosurgery for benign perioptic tumors: a retrospective multi-institutional study.
Dosimetric comparison between CyberKnife and GammaKnife hypofractionated radiosurgery for benign perioptic tumors: a retrospective multi-institutional study.

Purpose: We conducted a retrospective multi-institutional study to compared the dosimetric differences between CyberKnife (CK) and GammaKnife (GK) in treatment planning of hypofractionated stereotactic radiosurgery (hSRS) for benign perioptic tumors.

 

Methods: We selected 18 perioptic tumors (contact to optic nerve = 9; contact between optic nerve and optic track = 8; wrapped around optic nerve = 1) previously treated using CK between 2011 and 2015. The CK plan was generated using 4 or 5 dose-limiting auto-shells, one at prescription dose level, another at intermediate dose level for steeper dose fall-off, and the others at low-dose levels, with an optimized shell-dilation size based on our experience. The GK plans were also produced using the original contour set in two institutions (GK1 and GK2). Thus, three data sets of dosimetric parameters were generated and compared. hSRS was delivered in five fractions with a median marginal dose of 27.8 Gy (≈14 Gy in a single fraction, assuming an α/β of 3) to a median tumor volume of 3.1 cm3. All treatment planning goals was maximizing the minimum dose (Dmin) to tumor, while satisfying the dose-volume constraints criteria (Dmax < 25 Gy and V20Gy < 0.2 cc) of the optic apparatus (OA) as closely as possible.

Results: All treatment plans achieved a high level of CI (1.24 for CK, 1.27 and 1.25 for GK1 and GK2 plan, respectively; P=0.742), although the OA doses were well within the tolerated dose-volume limits in all plans. However, statistically significant differences in plan qualities were observed between the CK, GK1, and GK2 plans [Dmin, 22.87 for CK vs. 19.09 and 17.95 for GK1 and GK2 (p < 0.014); tumor coverage (CO), 94.39% for CK vs. 88.51% and 94.83% for GK1 and GK2 (p < 0.001), and gradient index (GI50), 3.39 for CK vs. 2.89 and 2.65 for GK1 and GK2 (p = 0.007)].

 

Conclusions: These results indicate that CK plans produced significantly high quality values of Dmin and CO than those produced by both GK plans (P<0.001). In particular, the wrapped around optic nerve case showed the largest difference, maintained dose-volume limit of the OA. However, the both GK plans achieved a level of GI50 (2.89 for GK1 and 2.65 for GK2) higher than the CK (3.39, p = 0.007). The GK plans achieved more rapid dose fall-off around the tumor than the CK plan and therefore saved more critical normal tissue.

Kyoungjun YOON (Korea, KOREA), Byungchul CHO, Jungwon KWAK, Doheui LEE, Weon Seop SEO, Do Hoon KWON, Seungdo AHN, Sang-Wook LEE, Chang Jin KIM, Sung Woo ROH, Young Hyun CHO
09:00 - 18:00 #17706 - Gamma knife surgery for Atypical and Anaplastic meningiomas: determination of irradiation dose based on MIB-1 index in addition to devise irradiation field.
Gamma knife surgery for Atypical and Anaplastic meningiomas: determination of irradiation dose based on MIB-1 index in addition to devise irradiation field.

Gamma knife surgery for benign meningioma can be said to have established its effectiveness, but the results of gamma knife surgery for atypical and anaplastic meningioma are not favorable . It seems that this is related not only to the tissue type of the tumor but also to the proliferation ability of the tumor cells which are very extensive. In 2009, Nakaya et.al. reported that Gamma knife surgery  for  meningioma increases the risk for recurrence when MIB-1 index exceeds 3%. Based on this report, we made a protocol to raise the dose according to the value of MIB-1 index with the minimum irradiation dose 15 Gy for atypical meningioma. and  in residual tumor after surgery, we made a strategy that the irradiation field was devised so as to cover the attachment area of the tumor before surgery to prevent marginal recurrence.We report the results and problems of the protocal and strategy.

13 patients with atypical and anaplastic meningioma who underwent gamma knife surgery at our institute  from January 1, 2012 to February 10 2017 

Male :8  Female :5  Median age: 69 y.o  (21 to 80 )  Median follow up period 28 month (5 to 57 )  Median tumor volume :2.93 ml (0.1 to 8.4 ml)  Median MIB-1 index :9.7% (3.4 to 29.1%)  Median irradiation dose :17GyRecurrence was observed in one case, but in other 12 cases local tumor control  was obtained. 

There are so many cases with high MIB-1 index, it is desirable to treat with high dose from the viewpoint of risk for recurrence.

Because the number of cases is small and the follow up period is short, it is necessary to accumulate more cases and long observation period.

 

Kawai HIDEYA (Akita-City, JAPAN)
09:00 - 18:00 #17739 - Long term results of stereotactic radiosurgery treatment for cavernous sinus meningiomas on multiple devices.
Long term results of stereotactic radiosurgery treatment for cavernous sinus meningiomas on multiple devices.

Introduction. Stereotactic radiosurgery (SRS) is an important treatment option for patients with cavernous sinus meningiomas and can be performed using various radiosurgical techniques. The purpose of clinical study was retrospective analysis of the efficiency of SRS and long-term results for cavernous sinus meningiomas.
Materials and methods. Linear accelerator «Trilogy + BrainLab» stereotactic radiosurgery was performed in 30 patients (8 males and 22 females; mean age - 52 years) with cavernous sinus meningiomas. Tumor volume ranged from 2.8 cc to 20.9 cc (median, 9.1 cc). 23 patients in LINAC group (76.7%) received SRS alone, and 7 patients (23.3%) had undergone surgery before SRS. CyberKnife(CK) SRS was performed in 12 patients (5 males and 7 females; mean age - 47 years, median tumor volume 13,6 cc). In CK SRS group only 3(25%) patients had surgery before. The marginal doses for the tumors were  for LINAC SRS 11 Gy to 12.5 Gy (median, 12.1 Gy), for CK SRS 18-25 Gy in 3-5 fractions. Median follow-up of patients was 42 months (range, 30-60 months).
Results Follow-up images showed a reduction in tumor size in 14 patients (46.7%), no further growth in 16 (53.3%) cases in LINAC group and decrease of the tumor size in 5 (41,6%) patients and stable tumor size in 7 (58,4%) patients in CK group. In both group 16 (38,1%) patients demonstrated improvement in their neurological condition. Other 61,9 % patients also had no worsening of their neurological status. None of the patients in both groups experienced post-radiation toxicity grade 2-3. patients.  

Conclusions. SRS − is an effective method of treatment for сavernous sinus meningiomas, that can be performed using various radiosurgical techniques providing tumor control without significant difference and with same quality of life outcome.

Vladyslav BURYK, Olga CHUVASHOVA (Kyiv, UKRAINE), Maris MEZECKIS, Igors AKSIKS, Dace SAUKUMA, Maris SKROMANIS, Jelena NIKOLAJEVA, Iryna KRUCHOK
09:00 - 18:00 #17822 - Outcomes after gamma knife radiosurgery for intracranial meningiomas.
Outcomes after gamma knife radiosurgery for intracranial meningiomas.

Intro: Gamma Knife Radiosurgery (GKRS) is both an important primary and adjuvant management strategy for patients with meningiomas. We analyzed outcomes in patients treated with GKRS and attempted to determine risk factors related to treatment failure and overall survival.

Methods: Between March 2014 and June 2018, 96 consecutive patients with a total of 143 meningiomas were treated with GKRS utilizing doses between 10-20 Gy. The series consisted of 74 women and 26 men. Median age was 63 years-old (Range, 29-87) and 48 patients had previous resection. There were 12 patients with 23 radiation induced meningiomas along with an additional 15 patients who were receiving reirradiation. In total, there were 32 posterior fossa, 22 middle fossa, 8 anterior fossa, 4 torcular, 4 intraorbital, 3 sylvian fissure, 40 convexity, 23 parasaggital, and 11 falcine meningiomas.

Results: At a median follow-up of 24 months (Range, 2-55) the overall local control (LC) rate was 88% with a mean time to progression of 46 months. When compared to patients with WHO Grade 2 or Grade 3 meningiomas, patients with Grade 1 meningiomas had significantly improved progression free survival (95% Grade 1 vs. 50% Grade 2 vs. 0% Grade 3, p < .001), disease free survival (100% Grade 1 vs. 75% Grade 2 vs. 33% Grade 3), and overall survival rate (97% Grade 1 vs. 70% Grade 2 vs. 33.3% Grade 3). Twelve patients had radiation induced meningiomas and were found to have significantly worse control compared to patients without radiation induced meningiomas (50% vs 90.5%, p<.001) and decreased mean time to progression at 27.4 months. Skull base location, dose, age, race, gender, previous surgery, or previous radiation treatment, did not affect LC, PFS, OS, or DFS on multivariate analysis.  

Conclusion: GKRS is an effective treatment modality for benign meningiomas. Survival and local control decreases with increasing tumor grade and radiation induced etiology.

Zaker RANA (New Hyde Park, USA), Troy DAWLEY, Michael SCHULDER, Anuj GOENKA
09:00 - 18:00 #17892 - PRELIMINARY RESULTS AFTER HYPOFRACTIONATED RADIOSURGERY WITH GAMMA KNIFE ICON FOR CAVERNOUS SINUS MENINGIOMAS.
PRELIMINARY RESULTS AFTER HYPOFRACTIONATED RADIOSURGERY WITH GAMMA KNIFE ICON FOR CAVERNOUS SINUS MENINGIOMAS.

Hypofractionated stereotactic radio-surgery allows physicians to treat larger volumes or lesions in the proximity of critical structures, in particular optical nerves and chiasma.

Using Gamma Knife Icon is possible to deliver treatments in frameless modality thanks to a Cone-Beam CT integrated with the machine, which assigns stereotactic coordinates coregistering MR-CT treatment plans to a reference CBCT acquired at the beginning of each treatment.

Between November 2017 and November 2018, 64 patiest with a meningioma underwent Gamma Knife radiosurgery in Fondanzione Poliambulanza in a frameless modality; of them 17 patients had a cavernous sinus meningiomas very close to optic pathways. The aim of the study is to validate the accuracy of hypocractionated treatments with Gamma Knife Icon analyzing the possible side effects.

Gamma Knife radiosurgery was delivered in frameless modality in 5 sessions with a mean prescription dose of 5 Gy per session and a total prescription dose of 25 Gy. Mean tumor volume was 7,910 ml (0,917 - 16,473 ml). Mean maximum dose to the optic apparatus was always below 5 Gy for each session. 

With a minimum follow-up of three months no patient presented a worsening of the visual function or the appearance of deficit of other cranial nerves. The first MRIs of follow up did not show edema. 

Very  preliminary experience suggests that hypo-fractioned radiosurgery with Gamma Knife Icon can be asafe treatment for tumors immediately close to segments of the optic apparatus.

Alberto FRANZIN (Brescia, ITALY), Lodoviga GIUDICE, Cesare GIORGI, Chiara BASSETTI, Ivan VILLA, Oscar VIVALDI, Mario BIGNARDI
09:00 - 18:00 #17794 - Rotating Gamma System (RGS) treatment of petroclival meningioma. Was that helpful for patients?
Rotating Gamma System (RGS) treatment of petroclival meningioma. Was that helpful for patients?

Purpose: Radiosurgery is widely accepted in management of benign intracranial tumors such as meningioma. Petroclival meningioma(PC) arise in the area surrounding the spheno-occipital synchondrosis. Because of its location, it can displace the brainstem and encase the surrounding critical neurovascular structures. Despite the advances in neurosurgical operative technique, the surgical resection still remains a substantial challenge. In the last decades, radiosurgery gave new hope for meningioma patients.The aim of the study was to retrospectively investigate and report our experience with RGS treatment of PC meningioma and compare our results to other radiosurgery systems as well.

Method:From 2007 to 2017, 75 treatments for PC meningioma was performed as primary indication or next to surgery. Single session treatment was carried out with RGS (GammaART 6000ND, San Diego, CA) device. Mean total volume was 6.23ccm (0.81-39.01ccm). Mean marginal dose was 12.25Gy (10-16Gy). After treatment, the patients were regularly examined. Mean follow up time was 63months (9-118months). Clinical symptoms and MRI findings were assessed. 

Results:Good clinical and radiological outcome was observed in majority of cases. After irradiation, we found that in 94% of patients, tumor volume decreased (19.7%) or controlled(74.3%). In 6% further action (repeat of irradiation or surgery) was necessary. One patient was passed away in complications caused by the tumor growth. In other cases, survival time was not affected by tumor itself. Good, acceptable life quality was found in 82% of patients. Symptoms were improved (12%) or were in stable, tolerable condition (70%). In 18% of cases symptom progression or new symptom was detected even the tumor volume was unchanged. Most of the clinical exacerbation were due to increasing pain of trigeminal neuralgia. These patients were reirradiated with a higher radiation dose or underwent open surgical procedure.

Conclusion:Our results suggest that in case of small- to medium-sized PC meningioma, single session radiosurgery is an acceptable alternative to surgery. Tumor volume and symptoms are highly controlled with this procedure. Reviewed our series and compared to previously published results we can conclude that RGS treatment is practically as effective as other radiosurgical system treatments. 

József Gábor DOBAI (Debrecen, HUNGARY), Bernadett SZŰCS, Gulyás LÁSZLÓ, Tamás HOLLÓ, Imre FEDORCSÁK, László BOGNÁR
09:00 - 18:00 #17806 - Visual outcomes after radiotherapy and radiosurgery for optic nerve sheath meningioma.
Visual outcomes after radiotherapy and radiosurgery for optic nerve sheath meningioma.

Introduction: Optic Nerve Sheath Meningiomas (ONSMs) are rare, benign neoplasms of the anterior visual pathway, accounting for 2% of orbital tumours. Left untreated, they may blind and disfigure patients. Currently, radiotherapy is preferred over surgery or observation, however the optimal modality of radiotherapy has not been established. The use of stereotactic radiosurgery in treating ONSMs has been limited due to the high radiation doses delivered to the optic nerve.

 

Methods: We performed a retrospective analysis of visual outcomes and side effects in ONSM patients treated with radiosurgery at three centres in Sydney, Australia, between 2000 and 2016 (n = 15). We also performed pooled data analysis of available studies, comparing visual outcomes between fractionated radiotherapy and hypofractionated radiosurgery (hfSRS, up to 5 fractions).

 

Results: In our cohort, a significant majority experienced improved visual field outcomes (p = 0.046), and stable or improved visual acuity (p = 0.0017) and colour vision (p = 0.015) after fractionated radiotherapy with an average follow up time of 46.5 months. When patients who had previous surgical procedures were excluded, no patient experienced worse visual acuity, visual fields or colour vision. Pooled data analysis with strict inclusion criteria revealed a significantly poorer visual acuity for patients receiving 3D conformal radiotherapy (3D-CRT) compared to those receiving fractionated stereotactic radiotherapy (FSRT). When all published studies were included, there was no significant difference between hfSRS and fractionated methods (3D-CRT, FSRT, intensity-modulated radiotherapy) for visual acuity, visual fields or tumour response. Rates of long term side effects were lowest in the hfSRS group.

 

Conclusion: These results support the use of stereotactic radiotherapy delivery, and suggest hfSRS is a viable treatment option for ONSM patients despite the higher radiation doses associated with each fraction. 

Christopher OVENS, Benjamin DEAN, Cecelia GZELL (SYDNEY, AUSTRALIA), Nitya PANATJALI, Benkamin JONKER, Michael O'CONNOR, Patrick ESTOESTA, Tatiana DE MARTIN, Clare FRASER
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P09
09:00 - 18:00

EPOSTER - 09 Metastases
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #16793 - A standardised method for use of the leksell gammaplan inverse planning module for metastases.
A standardised method for use of the leksell gammaplan inverse planning module for metastases.

Leksell GammaPlan version 10 and higher contains an inverse planning module, consisting of functions to automatically fill a target volume with shots and subsequently optimise their resulting dosimetry. A standardised method for using the inverse planning module was developed for metastases, using the following optimisation parameter weightings: {coverage 0.9, selectivity 0.1, gradient index (GI) 0.2, beam on time (BOT) 0.0} and nineteen plans produced using this method were compared to manually produced clinical plans.

The average parameters for plans produced using the optimisation module were; coverage 98.8%; Paddick conformity index (PCI) 0.85; GI 2.68, compared to coverage 99.4%; PCI 0.84; GI 2.69 for manual plans. Decay corrected BOT for plans produced using the optimisation module was on average 17% shorter than manual plans.

The standardised method for using the optimisation module has potential for shortening treatment times and planning times.  

Peter FALLOWS, Gavin WRIGHT (Leeds, UK), Peter BOWNES
09:00 - 18:00 #17862 - Brain metastases from renal cancer are sensitive to gamma knife treatment.
Brain metastases from renal cancer are sensitive to gamma knife treatment.

Objective:

Gamma knife surgery (GKS) is increasingly used in the treatment of brain metastasis (BM) from renal cell carcinoma (RCC) due to their resistance towards whole brain radiotherapy (WBRT). In lack of prospective studies, retrospective reviews are valuable.

 

Methods:

Between 2005 and 2015, 66 patients with 140 RCC BM from RCC were treated with GKS at Haukeland University hospital, Norway. The mean age was 62 y (range 26-83) and 41 (62.1%) patients were males. Total tumor volume was 5.30 cm3 (range 0.03 – 26.2) and mean prescription dose 21.3 Gy.

Results:

Local control was achieved in 117 (91.4%) and radiation induced edema occurred in 19 (14.8%) of the 128 BM with follow-up images. Median OS was 9.8 months (95 % CI 6.3 -13.4). Patients with 1 BM had the longest OS, 17.4 months (95% CI 6.8–28.0) compared to 16.6 (95% CI 5.2–27.9) and 4.8 (2.9–6.7) months for patients with 2 and 3 BM, respectively (p < 0.001). OS was longer for patients with KPS ≥ 70 vs. patients with KPS < 70 (p=0.048) and those treated with nephrectomy vs. not for their primary cancer (p=0.006). Intratumoral BM hemorrhage before GKS observed in 7 (10.6 %) patients was associated with poor OS, 4.6 months (95 % CI 3.0-6.1) vs. 10.9 months (95 % CI 5.2-16.6), p < 0.001. The number of BM, presence of intratumoral hemorrhage and prior nephrectomy remained significant factors for survival after multivariate analyses.

Conclusion:

GKS is a safe and effective treatment option in patients with BM from RCC. GKS seems to overcome the radioresistance observed towards WBRT. A reason may be the high vascularity of RCC-BM, similar to melanoma BM. The prognostic factors in the present study are in line with prior studies. A new finding is the poor survival associated with BM hemorrhage.

Bente Sandvei SKEIE (Bergen, NORWAY), Veronika LABUSOVA, Geir Olve SKEIE , Jan Ingemann HEGGDAL, Elisabeth LARSEN, Paal-Henning PEDERSEN, Per Øyvind ENGER
09:00 - 18:00 #17737 - Brain metastases radiosurgery: comparison of two irradiation tehniques.
Brain metastases radiosurgery: comparison of two irradiation tehniques.

Stereotactic radiosurgery (SRS) treatments can be performed on various devices: cyber-knife, linear accelerators (linacs), tomotherapy, gamma knife, particle accelerators. Every device has advantages over other. Linacs still remain one of the most common devices for SRS. Main advantage of linacs is multi leaf collimator (MLC). MLC can shape irregular fields, and form the best possible blocks for sparring organs at risk. Linacs can have, as add-on, another collimator for SRS treatments: cone collimator. Although it is not completely new feature of linacs, it is still not widely used. Cone collimator provides steep dose gradient, and because of it, dose to the brain is reduced. In theory, cone collimator should provide better sparring of brain tissue. In this work, in depth comparison of MLC and cone collimator have been performed in order to provide answer to questions: will cone collimator give statistical significant difference in dose to the brain in the case of single and multiple metastasis for small, medium and large lesion volumes, how accurate is cone algorithm, does simplified cone algorithm reduces optimization and calculation time and is there a difference for patient treatment time. 

27 patients with total of 120 metastasis have been selected into three groups and plan for micro MLC and cones have been calculated. Both plan types have same couch rotations, number of fields, start and stop gantry angles and linac (Varian EDGE). The first group consists of 30 comparison plans for lesions volume less than 1.0 ccm, second group consists of 30 comparison plans for lesions whose volume is between 1.0 and 2.5 ccm. Third group consists of 11 comparison plans for lesions whose volume is over 2.5 ccm.  Out of field dose measurement has been performed to test algorithm accuracy. All plans were planned on Varian Eclipse 13.7. MLC calculation algorithm is AcurosXB, cone algorithm is Eclipse Cone Dose Calculator (ECDC).

Adlan CEHOBASIC (Zagreb, CROATIA), Domagoj KOSMINA, Vanda LEIPOLD, Hrvoje KAUCIC, Andreas MACK
09:00 - 18:00 #17632 - CyberKnife dosimetric planning using a dose-limiting shell method for brain metastases.
CyberKnife dosimetric planning using a dose-limiting shell method for brain metastases.

Purpose: We investigated the effect of optimization in dose-limiting shell method on the dosimetric quality of CyberKnife (CK) plans in treating brain metastases (BMs).

Methods: We selected 19 BMs previously treated using CK between 2014 and 2015. The original CK plans (CKoriginal) had been produced using one to 3 dose-limiting shells: one at the prescription isodose level (PIDL) for dose conformity and the others at low-isodose levels (10%–30% of prescription dose) for dose spillage. In each case, a modified CK plan (CKmodified) was generated using five dose-limiting shells: one at the PIDL, another at the intermediate isodose level (50% of prescription dose) for steeper dose fall-off, and the others at low-isodose levels, with an optimized shell-dilation size based on our experience. A Gamma Knife (GK) plan was also produced using the original contour set. Thus, three data sets of dosimetric parameters were generated and compared.

Results: There were no differences in the conformity indices among the CKoriginal, CKmodified, and GK plans (mean 1.22, 1.18, and 1.24, respectively; P = 0.079) and tumor coverage (mean 99.5%, 99.5%, and 99.4%, respectively; P = 0.177), whereas the CKmodified plans produced significantly smaller normal tissue volumes receiving 50% of prescription dose than those produced by the CKoriginal plans (P < 0.001), with no statistical differences in those volumes compared with GK plans (P = 0.345).

Conclusions: These results indicate that significantly steeper dose fall-off is able to be achieved in the CK system by optimizing the shell function while maintaining high conformity of dose to tumor.

Kyoungjun YOON (Korea, KOREA), Byungchul CHO, Jungwon KWAK, Doheui LEE, Do Hoon KWON, Seungdo AHN, Sang-Wook LEE, Chang Jin KIM, Sung Woo ROH, Young Hyun CHO
09:00 - 18:00 #17707 - Efficacy of pre-operative stereotactic radiosurgery of brain metastases.
Efficacy of pre-operative stereotactic radiosurgery of brain metastases.

Preoperative stereotactic radiosurgery (pre-SRS) is a new strategy of  management for  brain metastases (BM). The goal of this analysis is to evaluate 6/12-month local control, overall survival and toxicity utilizing pre-operative SRS followed by surgical resection for patients with brain metastases.

Materials and methods. 35 patients with 83 BM (22 female and 13 male) have been treated using SRS & pre-SRS. 47 symptomatic metastatic lesions were pre-SRS in the series. 8 patients had NSCLC, 9 - BC, 7 - melanoma, 5 - renal carcinoma and 6 - other. Median target volume for combined treatment was 12,26 cc (4,074 - 57,098). Median of target dose was 18,94 Gy (12 and 24,36). Radiation dose was increased by approximately 20% compared to standard dosing as per RTOG 90-05 and was determined by tolerance of intact brain tissues. Pre-SRS followed by delivered surgical resection within 48 hours (Me=24 hours).

Results. All patients tolerated pre-SRS well, without any neurological deterioration, and surgical treatment was performed as scheduled. Median follow-up period was 11.3 months. Local recurrences were found in 3 cases. Local control was noted in 95.7% and 89.3% at 6 and 12 m respectively during follow-up. The median overall survival (OS) and 6 / 12 months OS rate were 17,1 months and 77,8/62,5 %, respectively.  Radionecrosis was present in 3 pts.

Conclusion: Pre-SRS confers excellent cavity local control with very low risk of RN. Pre-SRS confers excellent cavity local control with very low risk of RN.  Optimal dose, technique and  timing  for presurgical irradiation has not been established yet.

Andrey GOLANOV (Moscow, RUSSIA), Elena VETLOVA, Sergey BANOV, Natalia ANTIPINA, Valery KOSTJUCHENKO, Amayak DURGARYAN, Alexandra DALECHINA, Ivan OSINOV
09:00 - 18:00 #17887 - Fractionated stereotactic radiosurgery for brain metastases using Gamma Knife Icon.
Fractionated stereotactic radiosurgery for brain metastases using Gamma Knife Icon.

Treatment of large brain metastases in patients with poor prognosis or declining clinical conditions and treatment of metastases close to critical areas are still a challenge. Fractionated stereotactic radiosurgery (SRS) is one of the options. Gamma Knife treatments are usually delivered in single fractions, however few articles in literature report its use in fractional mode for these conditions.

Between November 2017 and October 2018 11 patients with brain metastases underwent fractionated Gamma Knife radiosurgery in Fondazione Poliambulanza: for seven patients the treatments were fractionated in three or five consecutive days (hypo-fractionated SRS), for four patients in two fractions (staged SRS) separated by and interval of about four/five weeks.

Median volume for large metastases prior to radiosurgery was 11,539 ml (range 7,334 – 26,777 ml), whereas for metastases close to critical areas was 4,549 ml  (range 0,815 – 5,548 ml). Median total margin dose for hypo-fractionated Gamma Knife treatments was 25 Gy (range 21 -.32,5 Gy), median dose per fraction was 7,5 Gy (range 5 – 9 Gy).  Median marginal dose for staged Gamma Knife treatments was 12 Gy (range 12 – 15 Gy) for both first and second fraction.

Results: in the staged SRS group all lesions decreased in volume at the second fraction, no complication or radionecrosis occurred between the two treatments. In the hypo-fractionated SRS group the survival rate is 71%, 57% and 35% at three, sex and nine months, respectively. One patient developed a seizure during recovery, instead in two cases there was an improvement in the clinical conditions at first follow up (3 months).

Conclusions: fractionated Gamma Knife SRS (hypo-fractionated or staged) is a valid and safe option for the treatment of metastases localized in critical sites or for large metastases in which surgery is less indicated.

Alberto FRANZIN (Brescia, ITALY), Lodoviga GIUDICE, Cesare GIORGI, Chiara BASSETTI, Oscar VIVALDI, Mario BIGNARDI
09:00 - 18:00 #17828 - HyperArc for stereotactic radiosurgery: comparison of delivery modalities.
HyperArc for stereotactic radiosurgery: comparison of delivery modalities.

Plan quality metrics for four different HyperArc modalities were investigated; two different energy modes 6FFFand 10FFF and different multi-leaf collimators systems, standard 120 leaves and high definition (HD-MLC) 120 leaves.  Twenty metastatic cranial patients treated with HyperArc were retrospectively planned using the Eclipse Treatment Planning System v15.5.

The cohort of patients included a range of patients with two to ten lesions (2.9cc to 26.0cc). Plans included four non-coplanar single isocentre arcs. Plans were optimised using standard objectives to meet clinical constraints based on SRS guidelines. All plans were normalized such that 80% of the highest prescription target volume received the prescribed dose.

Plan quality was evaluated by: volume of the brain receiving 20%,40% and 60% of the maximum PTV prescription for that patient; and median brain dose

All plans met local constraints and were suitable for treatment.

The brain dose was reduced in all plans using 6FFF together with HD MLC.  When compared with 10FFF HD-MLC selection, this was significant statistically at both the 20% and 40% values (p<0.05).  There was no significant variation in brain when comparing the 10FFF HD-MLC plan and 6FFF standard MLC plan, the median dose was reduced with the 10FFF plan.

10FFF plan with the standard MLC was least conformal. The median dose was also higher than the other plan situations, however this was not statistically significant. The number of PTVs did not influence optimal plan selection and plan quality metrics

The use of 6FFF and a HD-MLC provided the optimal solution to provide the sharpest dose gradient and to minimise brain dose.  The disadvantage of 6FFF to 10FFF is that delivery time is reduced from 24Gy to 14Gy per minute which may impact on PTV margins.  Current practice is being reviewed to produce two HD MLC plans at both energies to help determine plan selection.

Suzanne CURRIE (Glasgow, UK)
09:00 - 18:00 #17802 - Influence of the rotational patient setup errors on the quality of single isocenter SRS-VMAT brain metastases treatments.
Influence of the rotational patient setup errors on the quality of single isocenter SRS-VMAT brain metastases treatments.

Purpose

Stereotactic radiosurgery with VMAT (SRS-VMAT), using a single isocenter, is widely used nowadays for multitarget treatments providing highly conformal dose distributions and rapid dose fall-off outside the target volume. The purpose of this study is to determine the dosimetric effects of rotational errors on target coverage and organs at risk (OARs) in brain metastases cases.

Methods

Anonymized CT datasets of five patients with different number and size of multiple metastases were used. Single isocenter VMAT plans were generated for each patient using four noncoplanar arcs with 6MV FFF x-ray beams and Versa HD linear accelerator in Monaco (Elekta) TPS. Rotational errors of ±0.5°, ±1° and ±2° were simulated by rotating the plan dose distribution around the isocenter. Indices clinically used for plan evaluation were determined for the different degrees of rotational errors and compared with the reference values which correspond to zero rotation/error.

Results

For targets positioned away from the isocenter, rotational errors >1° produce geometric uncertainties greater than 1mm which may influence significantly plan evaluation indices leading to target coverage and conformity index deterioration (>10%).  Dose limits violations and differences >10% occur for Dmax, and D20mm3 for OARs in close proximity to targets. The degree of indices deterioration depends on the degree and direction of the rotational error as well as on target volume and target's distance from the isocenter.

Conclusions

For targets within a short distance from the isocenter, rotational errors of the order of 0.5° are negligible and high quality plans are achieved. In any other case, rotational errors may significant affect plan quality indices.

Acknowledgements

The research work was supported by the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. no.74112/2017 ).

Georgia PRENTOU, Andreas LOGOTHETIS, Eleftherios PAPPAS, Efi KOUTSOUVELI, Evangelos PANTELIS, Panagiotis PAPAGIANNIS, Pantelis KARAISKOS (Athens, GREECE)
09:00 - 18:00 #17652 - Integrating salvage hypofractionated radiosurgery with low-dose adjuvant bevacizumab for locally recurrent brain metastasis with high dose irradiation previously.
Integrating salvage hypofractionated radiosurgery with low-dose adjuvant bevacizumab for locally recurrent brain metastasis with high dose irradiation previously.

Background

Selection of the appropriate treatment for recurrent brain metastasis (BM) remains uncertain. Recent studies have demonstrated a significant response rate of fractionated stereotactic radiosurgery (FSRS) in locally recurrent glioma. However, radiation necrosis (RN) is a severe complication associated with salvage re-irradiation which may be treated with bevacizumab. The purpose of this research was to evaluate the efficacy and toxicity of FSRS combined with early use of low-dose bevacizumab as a new salvage treatment for locally recurrent BM with high dose irradiation.

Materials and methods

Patients with locally recurrent intracranial metastasis previously treated with SRS or WBRT with SRS were enrolled in this prospective study. The salvage FSRS dose ranged from 9.5 to 29 Gy in two to five sessions with 62–75% isodose line by CyberKnife according to the tumor volume, site, and previous irradiation dose. Bevacizumab was prescribed to all patients within 24 hours after completion of the treatment for four cycles (5 mg/kg, 3-week intervals). Magnetic resonance imaging (MRI), Karnofsky Performance Scale (KPS), adverse events and associated clinical outcomes were recorded. The primary objective of this study was to identify the overall survival after salvage treatment. Secondary objectives included clinical response (KPS), imaging response (MRI)and treatment-related adverse events.

Results

From December 2009 to October 2016, 24 patients were enrolled. Nine received WBRT followed by SRS, and 15 underwent SRS before diagnosed with recurrent BM. The median 1-year overall survival (OS) after salvage SRS was 87.5%. Twenty-three (96%) patients had a positive imaging response within a range of 6 to 22 cm3(median 14 cm3, p= 0.032, paired t-test). Significant clinical improvement was achieved (p<0.05, best KPS paired t-test). Grade 1/2 fatigue was observed in 8 (33%) patients followed by headache, hypertension, and nausea. Grade 3 fatigue and headache occurred in 1 patient. No grade 4 toxicity was observed.

Conclusions

Salvage FSRS with early use of low dose adjuvant bevacizumab treatment showed favorable clinical and radiologic control with manageable toxicity for locally recurrent brain metastasis patients who underwent high dose irradiation previously. The diagnosis of RN and LR after salvage FSRS merit further study.

Xin WANG, Huaguang ZHU (Shanghai, CHINA), Chaozhuang WANG, Jing LI, Wenqian XU, Lei SUN, Li PAN, Jiazhong DAI, Yang WANG, Yun GUAN, Enmin WANG
09:00 - 18:00 #17808 - Machine learning binary classification task for overall survival prediction in patients with brain metastases.
Machine learning binary classification task for overall survival prediction in patients with brain metastases.

The aim of this study was to predict overall survival in patients with brain metastases  after stereotactic radiosurgery and identify the prognostic factors using machine learning (ML) approach.

1023 patients treated with SRS between January 2005 and December 2017 were analyzed. 26 features (clinical, biological and morphological) were selected to develop a prognostic model  to predict overall survival for these patients. The target variable was time from the date of oncological diagnosis to the date of death. The data were divided into two sets: a training dataset and a test dataset. The training dataset consisted of 577 patients with different features, for which the target variable was known. The overall survival classes were: less than 8 months (292 patients), more than 10 months (285 patients). The second class ( OS > 10 months) included 92 patients that were alive at the day of the analysis. Splitting the group of patients on those classes supports class balancing and minimizes overfitting probability. The machine learning technique “Gradient boosting” was used to identify the favorable prognostic factors associated with long term overall survival.  The 5 - folds cross validation technique was performed to estimate the accuracy of the predictive model.

The most significant features were: age at the time of diagnosis, total volume of brain metastases, maximum metastasis volume, time from primary  diagnosis to brain metastases, time from brain metastases to the first radiosurgery. The accuracy of the classification model was 0.81. The accuracy computed from the confusion matrix was 0.80. The predictor had an average area under the curve (AUC) of 0.87.

To classify patients  into risk classes is the important step in making therapeutic decisions. The predictive model demonstrates accuracy of the brain metastases patients classification. Machine learning techniques seem to be a very promising tool for clinical decision making. But the principal challenge and the key ingredient of successful application of ML in radiation oncology  is data collection from the multimodal data sources. ML techniques will be fully integrated in clinic routine only if it combines with modern databases provided routine data collection.

Gleb VAZHENIN, Alexandra DALECHINA (Moscow, RUSSIA), Sergey BANOV, Pavel RYABOV, Valery KOSTJUCHENKO
09:00 - 18:00 #17643 - Mask-based, fractionated radiosurgery for brain metastases using gamma knife icon.
Mask-based, fractionated radiosurgery for brain metastases using gamma knife icon.

Gamma Knife Icon allows mask-based, fractionated brain radiosurgery, as well as standard, frame-based treatment. Leeds was one of the first centres in the world to start using it in December 2015. Between then and December 2017, 58 patients with brain metastases were treated in this way (median age 67, range 27-89). Standardised fractionation was used (either 27Gy in 3 in 64% or 30Gy in 5 in 33%, largely depending on volume). Two patients (3%) had single fractions using a mask to avoid having a frame. Unlike some centres that “stage” fractions with 1-2 week gaps, treatment was given on consecutive working days using a single treatment plan (planning MRI within 72 hours of first fraction).

 

Lung (41%), breast (24%) and gastrointestinal (22%) were the commonest primary tumour sites. The main indication for mask-based treatment was size (in 74%) - median 16cm3, IQR 12.3 - 19.7cm3, maximum 30.4cm3 in this group. Others included re-treatment (14%), eloquent location such as brainstem (9%) or patient choice (3%). Median KPS - 90 (range 70-100). Solitary metastasis in 53% of cases, multiple (range 2-5) in the remainder.

 

Detailed follow up was available for 43 patients. 94% of those on steroids reduced them after treatment. 85% stopped them completely. None had a permanent neurological deficit caused by treatment. 9% developed leptomeningeal disease during follow up. 26% had local failure at a median of 300 days. 40% had changes felt to represent treatment effects but this was only symptomatic in 9%. Only 2% required admission for these (one of which was re-treatment in an eloquent location).

 

Median overall survival was 12.2 months. Survival was not significantly different between the 3 or 5 fraction groups (p=0.74), target volumes greater or less than a 3cm diameter sphere (p=0.32), or total treated volumes greater or less than 20cm3 (p=0.51).

Paul HATFIELD (Leeds, UK), Gavin WRIGHT, Finbar SLEVIN
09:00 - 18:00 #17907 - Multiple Brain Metastases Radiosurgery with Gantry-Based Linac.
Multiple Brain Metastases Radiosurgery with Gantry-Based Linac.

Purpose 

Evaluate tolerance, toxicity and survival in patients with multiple brain metastases.

Material and Methods

Between Nov'16&Dec'17,24patients were treated with SRS.Frameless Brainlab System was utilized. Treatment planning was performed using Elements TPSv1.5(BrainLab). Patients were positioned on a6D couch. Radiosurgery was given by Novalis Tx accelerator HDMLC-IGRT with ExacTracV6 using 6 MV photons. Early and late toxicities as well as survival were evaluated. Patients with up to 5metastases were compared with te ones with6 or more, and  the ones with a tumor volume<10cc were compared with the rest with>10cc tumor volume. OS from SRS until last follow up or death, and progression-free survival(PFS) from SRS until first brain progression or last follow up, were estimated by the Kaplan-Meyer method.

Results

Mean age:54.2years[10.3-73.9]and mean follow-up8.16 months[3.2-16.6].The mean number of lesions per patient was 7[2-23] while the average volume of irradiated metastases was 1.34 cc[0.02-20.8].The prescribed dose was 22.2Gy[20.0-35.0] in1-5 fractions.5 patients were re-irradiated because of tumor regrowth(22 lesions)or new lesions(12 lesions); Of the24 patients,19 showed no symptoms of early toxicity whereas the remaining 5 presentedG1-2 toxicity .Late toxicity was evaluated in19 patients who survived for more than3 months. Of the 19patients,12did not show any toxicity while the remaining group presented G1-2 toxicity .No differences were found in patients with5 or more metastases regarding the presence or absence of toxicities, or related to fractioning.The overall survival(OS) for the24 patients at6 months was71%, and at one year59%. No differences were found in the OS of patients with five or moremetastases when compared with patients with less than five lesions(Cox-Mantel test, p = 0.806); There were no differences when comparing patients with a total volume of metastases<10cc and ≥10cc(p=0.865). The progression-free survival at6 months was89% and at one year62%. No differences were found in PFS related to the number of metastases(p=0.982) or to the total volume of metastases(Cox-Mantel test, p = 0.296).

Conclusion

Results suggest that irradiation to multiple metastases is safe,showing acceptable toxicity and survival.
If well in literature a detrimental inOS is described with a total tumor volume>10cc, we didn't find these difference.

Pablo CASTRO PENA (Cordoba, ARGENTINA), Daniel VENENCIA, Oscar MURIANO, Lourdes SUAREZ VILLASMIL, Silvia ZUNINO
09:00 - 18:00 #17762 - Neoadjuvant stereotactic radiosurgery for brain metastases; a novel sequencing approach.
Neoadjuvant stereotactic radiosurgery for brain metastases; a novel sequencing approach.

In modern oncology, therapeutic advances have been made in the management of brain metastases. Local therapies such as surgery and stereotactic radiosurgery (SRS), are currently standard of care for patients with oligo-metastatic or symptomatic brain disease. Whilst randomised evidence supports postoperative SRS for optimising local control, this treatment method has known challenges such as accuracy of radiotherapy target delineation, relatively high rate of leptomeningeal disease (LMD) and radiation necrosis (RN). Neoadjuvant radiosurgery (NaSRS) is an emerging sequencing approach with promising results for local control and toxicity. We performed a retrospective review of clinical records of thirteen patients who were treated with NaSRS followed by surgery from May 2017- October 2018. The median follow up was 7.8 months (range 0.4-16.1). The median age was 58.5 (range 45-72). Majority had primary Non-Small Cell Lung Cancer (62%) followed by Melanoma (31%) and Colorectal Cancer (7%).  One patient died of unrelated cause the day after SRS and never had surgery. Two patients (15%) had received whole brain radiotherapy prior to NaSRS. Of the remaining 12 patients, the interval between NaSRS and surgery was 1-20 days (mean 6.5). The most common dose fractionation schedule was 20Gy in 1 fraction and 24Gy in 3 fractions to the covering 80-90% isodose using Linac based SRS technology. Majority of targets were in the supra-tentorial space (80%), with only two patients with cerebellar lesions. At time of last follow up all treated patients (100%) had local control along the surgical cavity on imaging. Five patients (38%) had distant failure within the brain. At date of last follow up 9 patients (70%) were still alive. There was no reported incidence of LMD or RN related to the treated site. One patient developed a cerebral abscess 12 weeks after surgery. No other grade 3 or 4 toxicities were recorded.

Conclusion: Whilst the numbers in this cohort is relatively low and longer follow up is required, the results are promising and supportive of emerging data which suggest that NaSRS is an effective and safe sequencing strategy for select group of patients with brain metastases. The advantages of this approach appear to relate to local toxicity and reduction in leptomeningeal spread when compared with surgery and postoperative SRS. 

Neda HAGHIGHI (Melbourne, AUSTRALIA), Damien TANGE, Cristian UDOVICICH
09:00 - 18:00 #17767 - Personalized treatment options for patients with large cerebellar metastases by Gamma Knife radiosurgery.
Personalized treatment options for patients with large cerebellar metastases by Gamma Knife radiosurgery.

OBJECTIVE: To report our experience in patients with large cerebellar metastases for single-session, multiple-session or staged Gamma Knife radiosurgery (GKRS); and the evaluation of its efficacy and toxicity.

 

METHODS: From January 2017 to October 2018,826 patients with brain metastases underwent GKRS at our hospital. Among them, 25 patients with cerebellar metastases(maximal diameter≥2cm) were treated with single-session, multiple-session or staged GKRS. Individualized treatment strategy was chosen according to prior treatment history,size and location of tumor, or tumor harboring gene mutation. Dose selection was based on various factors including tumor size, previous history of radiation, or proximity to critical structure nearby. Overall survival (OS) and intracranial progression-free survival (PFS) were measured from the date of brain metastases treated by GKRS.

 

RESULTS: The median age was 64 years (range 42-78 years), and the median Karnofsky performance status (KPS) scoce was 70. Thirteen patients (52%) had non-small cell lung cancer. Fourteen patients (56%) underwent treatment with hypofractionated GKRS or staged GKRS, whereas 11 patients (44%) underwent single session GKRS. The median OS was 10.9 months (95% CI: 6.4-17.7). For staged treatment, median tumor volumes at the first and second GKRS were 11.9 cm3(range 3.1- 30.2 cm3) and 9.3 cm3 (range 1.7-26.1 cm3). Twenty patients died, and five patients were still alive at the time of the last follow-up. Sixteen patients (80.0%) died from systemic causes, two (10.0%) from neurologic causes, and two (10.0%) of unknown causes. Radiation necrosis developed in two cases 8.0%) during the follow-up period, one case with CTCAE grade 2 and one case with CTCAE grade 3.

 

 

CONCLUSIONS: Fractionated and staged GKRS are safe and effective options for large, unresectable cerebellar metastases. Prospective studies are necessary to validate the findings in this study. 

Ying TONG, Ping LAN (Hangzhou, CHINA)
09:00 - 18:00 #17902 - Plan Quality Comparison of HyperArc and Elements Platforms for Single Isocenter Multiple Metastasis Single Isocenter Radiosurgery.
Plan Quality Comparison of HyperArc and Elements Platforms for Single Isocenter Multiple Metastasis Single Isocenter Radiosurgery.

Background: Radiosurgery to multiple intracranial metastases is a rapidly increasingly employed treatment modality in an era of increasing survival for patients with stage IV cancer.  Several single-isocenter treatment planning solutions have been developed for planning efficient radiosurgery to multiple metastases. Two of the most advanced are the HyperArc (Varian Medical Systems) VMAT-based and Elements (BrainLab) DCA-based platforms. Each is designed to streamline and optimize complex radiosurgical treatment planning.

Methods: Fifteen multiple metastases (n = 4 - 10) radiosurgery cases were planned in HyperArc (HA) and Elements (MME) at institutions with leading expertise in each’s respective treatment planning and delivery (UAB and Thomas Jefferson University). All plans had a single isocenter and used a Varian linac equipped with high definition MLC. HA plans were generated with either both two and four non-coplanar VMAT arcs with 10MV flattening filter free (FFF) beam.  MME plans used four to nine non-coplanar dynamic conformal arcs and a 6MV FFF beam.  Prescription doses ranged from 14 to 24 Gy in a single fraction. Each target was planned to receive the prescription dose to at least 99% of target volume. Plans were evaluated according to standard radiosurgery metrics including conformity index (RTOG and Paddick) for each target, surrogate radionecrosis risk (V12Gy & V8Gy), and low dose spill (V5Gy and mean brain dose). Plan modulation and delivery times were also compared.

Results:  Conformity, V12Gy, V8Gy, V5Gy, and mean brain dose were favorable for HA plans (either 2 arc or 4 arc) for all cases (p<0.001 for all comparisons). 4-arc HA plans were overall superior to 2-arc HA plans for all metrics except for mean dose, where they were similar, and in delivery time, where they required an additional sixty seconds of delivery.

Conclusion: Both HA and MME were able to create clinically acceptable intracranial radiosurgery treatment plans. However, for single-isocenter linac-based multiple metastasis intracranial radiosurgery, VMAT-based HA facilitated favorable conformity, V12Gy, V8Gy, V5Gy, and mean brain dose compared to DCA-based MME plan.  

Rodney SULLIVAN, Evan THOMAS (BIRMINGHAM, USA), Richard POPPLE, Haisong LIU, James MARKERT, David ANDREWS, Wenyin SHI, Yan YU, John FIVEASH
09:00 - 18:00 #17817 - Post metastasis srs delayed radiation change mimicking recurrent disease: the ghost lesion.
Post metastasis srs delayed radiation change mimicking recurrent disease: the ghost lesion.

Post gamma knife SRS for metastatic disease can result in localized delayed recurrent gadolineum enhancement, many months to years after the initially treated lesion had completely resolved. If not recognized as delayed radiation change at the primary treatment site, this can easily be mistaken for recurrent malignancy and therefore initiate recurrent un-necessary treatement, including SRS.

Stephen HOLMES (honolulu, USA)
09:00 - 18:00 #17871 - Preoperative Gamma Knife radiosurgery for recurrent brain metastases.
Preoperative Gamma Knife radiosurgery for recurrent brain metastases.

Introduction:

Whole brain radiation (WBRT) impairs neurocognition. Resection of brain metastases (BM) without additional radiation therapy yields a high local failure rate. Postoperative stereotactic radiosurgery (SRS) maximizes local control while minimizing the risk of neurocognitive deterioration. Drawbacks of postoperative SRS include uncertainty in target delineation, potential delay in the administration of SRS and intraoperative risk of tumor spillage. Preoperative SRS might address these potential drawbacks. We present our experience with preoperative Gamma Knife radiosurgery (GKRS) for recurrent BM.

Material and Methods:

Between June 2016 and January 2019, 16 patients (male 5, female 11; mean age 62 years (range 21-79 years) underwent preoperative GKRS. Previous treatments were GKRS (9 patients), SRS (4 patients), WBRT (2 patients), resection and postoperative SRS (1 patients). Primary tumors were NSCLC (9 patients), SCLC (2 patients), melanoma (2 patients), breast cancer (2 patients), oesophageal cancer (1 patients). A dose of 18-20 Gy, was prescribed to the isodoseline (mean 44,7%; range 40-53%) covering 99-100% of the target. All patients had follow-up in our center with MRI scan as long as clinical meaningful.

Results:

Mean follow-up was 9,8 months (range 0,5-31 months). In all patients, the resection was performed as scheduled on the next day following preoperative GKRS. There were 2 surgical complications: seizures immediately postoperatively and 1 patient needed admission to intensive care because of extensive edema around the resection cavity. Two patient developed leptomeningeal disease after 3 and 4 months respectively. Six patients developed a local / marginal recurrence after median 6,8 months (range 2,0-14 months). Six patients died after median 4,3 months (range 0,5-24 months) due to leptomeningeal disease (2 patients), local recurrence (1 patients), systemic disease (1 patient), pneumonia (1 patient). Cause of death was unknown in 1 patient. 

Conclusion:

Preoperative GKRS for recurrent brain metastases is well tolerated. A randomized trial comparing preoperative GKRS versus postoperative SRS is warranted.

Patrick HANSSENS (Tilburg, THE NETHERLANDS), Guus BEUTE, Suan Te LIE, Liselotte LAMERS, Jeroen VERHEUL, Bram VAN DER POL, Diana GROOTENBOERS, Hilko ARDON, Hazem AL-KHAWAJA, Wouter VERFAILLIE, Wim DE JONG, Jannie SCHASFOORT - VAN DEN TILLAART
09:00 - 18:00 #17889 - Prescription Estimation of Postoperative Brain Metastasis Stereotactic Radiosurgery (SRS) with Dose Energy Density Distribution Index (DEDDI).
Prescription Estimation of Postoperative Brain Metastasis Stereotactic Radiosurgery (SRS) with Dose Energy Density Distribution Index (DEDDI).

Introduction: There were three options of clinical approach for brain metastasis patient. The first is the execution target resection by neurosurgeon, the second is the application of radiosurgery only, and the third is the combination of first and second procedures, which could be at different temporal sequence selection by alternating the order of resection surgery and stereotactic radiosurgery. However, the difference between these two sequences could require different dose prescriptions. In this study, the prescription dose distribution effect was analyzed by a dose energy density distribution index. Method and Materials: The selected patient was underwent the resection of the brain metastatic tumor from prostate cancer. The original target size showed in MRI with contrast was about 2cm in diameter.  It is assumed that the margin between 1 cm radius and 2cm radius around the target before resection was considered to be irradiation region for postoperative SRS. The prescription of residual region after resection was treated as isotropic shrink from the original tumor target, which is at the level of 2cm in diameter. And the geometric comparison was done by registration of image sets at different temporal point. The dose energy density distribution index (DEDDI) was computed to reach the prescription requirement at the scenario of treating without target resection. And DEDDI was defined to be dose rate with energy spectrum to reflecting the dose delivery pattern including kinetic temporal factor.  The variation between these two approaches was also estimated with geometric perturbation analysis in 1mm scale step. Results: For the selected plan, including the resection target and volumes with prescription range from 24Gy to 15Gy, the values of DEDDI ranged from 0.43cGy/s/CC to 0.179cGy/s/CC and excluding the 2cm target, the values of DEDDI ranged from 8.99cGy/s/cc to 0.05cGy/s/CC; Based on the postoperative plan, consider the volumes with prescription of 18Gy to 10Gy, the values of DEDDI ranged from 0.33cGy/s/CC to 0.221cGy/s/CC. Plotting these two curves in same coordinate system, the cross point was at about 17Gy. Conclusion: Dose Energy Density Distribution Index could be applied to estimate the prescription for postoperative brain metastatic target. Further prescription improvement could be done by validation with clinical outcome data.

Kaile LI (Hagerstown, USA), Arnold ABLE
09:00 - 18:00 #17849 - Radiation therapy and cognitive functioning: long term impact on patients with brain metastasis.
Radiation therapy and cognitive functioning: long term impact on patients with brain metastasis.

Introduction: Although in recent years the interest in impact of radiation therapy (RT) on neurocognitive functioning and quality of life (QoL) has become one of important issues in research and when choosing treatment for patients with brain metastases, the impact for long-term survivors  is still not clear. The main aim of this study is therefore to evaluate long-term neurocognitive and QoL outcomes in patients treated with RT for brain metastases.

Methods: Patients had a neurocognitive and QoL evaluation before RT, 3, 6 and 12-45 months after RT. A neurocognitive battery of tests  was used for neurocognitive and EORTC QoLC30 and BN20 for QoL evaluation. Mini mental state examination (MMSE) and Rey Auditory Verbal Learning Test (RAVLT) were considered in this work. Differences between baseline and follow up scores were analyzed with ANOVA test.

Results: 34 patients were enrolled (median age 52). Most of them had breast cancer as primary tumor (55%). 60% had no neurological symptoms at diagnosis. 9% of patients received whole brain RT (median dose 30Gy)and 91% had stereotactic RT (median dose 21Gy). During treatment no acute toxicities were reported.

33 patients completed baseline evaluation, 26 at 3 months, 19 at 6 months  and 10 between 12-45 months.

Baseline MMSE and RAVLT indicated no neurocognitive deficit in 97% and 74% of patients. Global QoL was 37.37, mean BN20 score was 24.

Comparison with follow-up scores showed no significant changes in MMSE (p = 0.16). Both immediate and delayed recall in the RAVLT significantly changed (p<0.01) with marked increase of scores up to 6 months. No significant changes over time were found in Global QoL and BN20 (p=0,24; p=0,55).

Conclusions. There were no changes in global neurocognitive functioning in long-term survivors. Specifically for verbal memory statistically significant improvement was observed. QoL did not change through the time. 

Milda CERNIAUSKAITE, Valentina PINZI (Milan, ITALY), Michela BUGLIONE, Cecilia IEZZONI, Laura FARISELLI
09:00 - 18:00 #17761 - RADIONECROSIS IN PATIENTS RECEIVING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES.
RADIONECROSIS IN PATIENTS RECEIVING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES.

Aim: To examine factors contributing to radiation necrosis (RTN) in patients receiving stereotactic radiosurgery (SRS) for brain metastases

Methods: Single institution series of 51 consecutive patients with intracranial metastases undergoing SRS.  Follow-up imaging was on standard protocol of MRI 6 weeks post-treatment then 3 monthly thereafter.

Results: Median age at diagnosis 59 years (range 24-86) with median survival of 19.4 months (range 0.9-53.4).  Demographics include 56.9% female, 43.1% male, and 9.8% (n=5) had brain metastases at the time of initial diagnosis.  Histopathology included: lung 37.3%, breast 17.6%, melanoma 11%, colorectal 5.5%, and other malignancy 25.5% (adenoid cystic, sarcoma, prostate, transitional cell, and renal cell).  Craniotomy was performed in 80% (N=41) of patients prior to SRS for at least one intracranial lesion.  De novo SRS was delivered to 82 metastases (85%) and cavity SRS was delivered in 65 cases (44%)

Rate of RTN was 20% (n=10). Diagnosis was based on histopathology in 6 patients, MRI and FET-PET in 1 patient, and MRI alone in 3 patients.  Patients with RTN had the following features: 50% (N=5) had concurrent systemic therapy (doublet therapies including Herceptin and pertuzumab, dabrafenib and trametinib, or androgen deprivation therapy).  One patient with RTN also had whole brain radiotherapy to a dose of 30Gy/10# with a boost of 6Gy/3# to the tumour bed 11 months prior to SRS.   Of the patients with RTN 60% (N=6) were asymptomatic and 40% (N=4) were symptomatic. Decompression surgery was needed in 4 patientsfor symptomatic relief.

Median survival of patients with RTN was 37.5 months (range 9-53) compared to 10.4 months (range 0.9-53.4) in patients without necrosis (P=0.0391).

Conclusion: RTN occurred in 20% of included patients in this series. The presence of necrosis may be prognostic for improved median survival. Further analyses are planned to investigate other contributing factors.

Philippa ELL (Sydney, AUSTRALIA), Yael BARNETT, Peter EARLS, Louise EMMETT, Michael RODRIGUEZ, Cecelia DE GZELL
09:00 - 18:00 #17881 - Radiosurgery for Brain Metastases: Multicentric Retrospective Analyses.
Radiosurgery for Brain Metastases: Multicentric Retrospective Analyses.

Background and Objectives

Stereotactic radiosurgery (SRS) in brain metastases is a standard strategy to delay or avoid whole-brain irradiation (WBRT) and its associated toxicities. This multicentric retrospective study analyzes results with linear accelerator (LINAC)-based SRS in brain metastasis.

 

Material and Methods

Between January 2016 and November 2018, 355 brain metastases in 109 patients were treated with SRS. All treatments were delivered using a stereotactic LINAC-based SRS. We evaluated toxicity using the common terminology Criteria for Adverse Events v4.0 (CTCAE), survival and local control.

 

Results

109 patients had a median of 3 lesions (1-20). The median dose prescribed to the PTV margin for SRS was 24 Gy (18-30) in 3 fractions (1-5). Median follow-up was 10 months. Distribution by histology 44% lung, 27% breast,10% melanoma, 6%renal, 13% others. Local control (LC) rate was 95%. Overall survival rates were 80%, 60% and 49% at 3, 6 and 12 months respectively with a median OS of 9 months. Adverse events occurred in 60% of the patients, G1 headache being the most frequent symptom and we observed only 5% G2 brain edema that resolved with steroids.

 

Conclusion

In this retrospective, multicentric on radiosurgery for brain metastasis, we conclude that LINAC-based SRS is an effective and well tolerated treatment strategy in patients with brain metastases.

Lucas CAUSSA (Córdoba, ARGENTINA), Leticia ALVARADO, Ofelia PEREZ CONCI, José Máximo BARROS, Jorge CHIOZZA, Ignacio SISAMON, Juan GALARRAGA, Sebastián PIAGGIO, Daniel DAVALOS, Diego FERNANDEZ, Egle AON, Diego FRANCO, Edgardo GARRIGO, Caroline DESCAMPS, Enrique HERRERA, Emilio MEZZANO, Gerardo Gabriel HEINRICH, Maria Fernanda DIAZ VAZQUEZ, Gustavo FERRARIS
09:00 - 18:00 #16747 - Re-irradiation in recurrent high-grade gliomas: A systematic analysis of treatment technique with respect to survival and radionecrosis outcomes.
Re-irradiation in recurrent high-grade gliomas: A systematic analysis of treatment technique with respect to survival and radionecrosis outcomes.

Background 

Re-irradiation may be considered for select patients with recurrent high-grade gliomas (WHO Grade III and IV). Treatment techniques include conformal radiotherapy employing conventional fractionation, hypofractionated stereotactic radiotherapy (FSRT), and single-fraction stereotactic radiosurgery (SRS). 

Methods

A systematic review was performed to identify relevant articles pertaining to re-irradiation of recurrent high-grade gliomas from 1992 to 2018. A population-weighted, pooled multiple regression analysis of publications was performed to evaluate the relationships between re-irradiation technique and median overall survival (OS) and radionecrosis outcomes. 

Results 

Seventy-nine published articles were analyzed, yielding a total of 3738 patients. Across all studies, initial treatment was external beam radiotherapy to a median dose of 60 Gy in 30 fractions, with or without concurrent chemotherapy. On multivariate analysis, there was a significant correlation between OS and radiotherapy technique after adjusting for age, re-irradiation biologically equivalent dose (EQD2), interval between initial and repeat radiotherapy, and treatment volume (P < .0001). Adjusted mean OS was 12.1 months (95% CI, 11.8–12.4) after SRS, 9.9 months (95% CI, 9.4–10.3) after FSRT, and 9.0 months (95% CI, 8.6–9.4) after conventional fractionation. There was also a significant association between radionecrosis and treatment technique after adjusting for age, re-irradiation EQD2, interval, and volume (P < .0001). Adjusted radionecrosis rates were 7.1% (95% CI, 6.6–7.7) after FSRT, 6.2% (95% CI, 5.6–6.6) after SRS, and 1.1% (95% CI, 0.5–1.7) after conventional fractionation. A greater interval between initial and repeat radiotherapy was associated with improved OS (0.25 month greater OS per month interval) (p<0.0001) and decreased RN rate (reduction of 0.23-0.48% per month interval) (p<0.0001).

Conclusions

The published literature suggests that OS is highest after re-irradiation using SRS, followed by FSRT and conventionally fractionated radiotherapy. Whether this represents superiority of the treatment technique or an uncontrolled selection bias is uncertain. The risk of radionecrosis was highest in FSRT followed by SRS and conventional radiotherapy however was acceptably low for all modalities overall. Re-irradiation is a feasible option in appropriately selected patients.

Mihir SHANKER (Brisbane, Australia, AUSTRALIA), Benjamin CHUA, Catherine BETTINGTON, Matthew FOOTE, Mark PINKHAM
09:00 - 18:00 #17667 - Retrospective audit of the first 10 patients treated with SRS for multiple brain metastases: comparison of multi-isocentres forward planned and mono-isocentre inverse planned techniques.
Retrospective audit of the first 10 patients treated with SRS for multiple brain metastases: comparison of multi-isocentres forward planned and mono-isocentre inverse planned techniques.

The JLGK0901 study demonstrated that stereotactic radiosurgery (SRS) without whole brain radiotherapy in patients with 5-10 brain metastases is non-inferior to that in patients with two to four brain metastases. Based on this result, our centre recently introduced SRS for patients with limited volume multiple brain metastases.

Currently, we plan SRS treatment with the Brainlab iPlan software which uses forward planned conformal static arcs (CSAT). Brainlab Elements planning software uses a set of multiple dynamic conformal arcs (DCAT) to calculate an inverse plan which targets up to fifteen lesions at once with a single isocentre.  Planning time is reduced from days to a matter of hours.

Materials: We performed a comparison of the multi-isocentres and mono-isocentre dosimetry for the first 10 patients that had 4 or more brain metastases (total volume <15cc). To assess plans, the Inverse Paddick Conformity Index (CI) and V12Gy dose-clouds for every treated lesion were calculated and compared as well as mean brain dose. Estimated treatment delivery times were also calculated.   

Results: Overall CIs and V12Gy of 49 treated metastases from 10 eligible patients were analysed. Mean forward planned CSAT CI was 1.62, while the mean inverse planned DCAT CI was 1.40. Mean mono-isocentric CI was superior for every patient. There was no significant difference in the V12Gy dose cloud between the plans: 2.15cc for forward planned vs 2.08cc for inverse planned. Mean brain dose was slightly higher for the mono- versus the multi-isocentric technique: 1.66Gy vs 1.46Gy, respectively. Mean estimated overall treatment delivery time was 6 times longer for multiple isocentres compared to a single isocentre. 

Conclusions: Inverse planned mono-isocentric DCAT SRS can produce at least a comparable dosimetry relative to multi-isocentric CSAT. It is expected to enhance patient experience due to its shorter treatment delivery time.  Adequate corrections to avoid rotational errors are required.

Natalia MITINA (Gold Coast, AUSTRALIA), Yurissa IKEDA, Emma MARRINAN, Jessica CARUSO, Joanne MITCHELL
09:00 - 18:00 #17663 - Stereotactic radiosurgery for the treatment of esophageal carcinoma brain metastases.
Stereotactic radiosurgery for the treatment of esophageal carcinoma brain metastases.

Object:

The authors evaluated the results of stereotactic radiosurgery (SRS) for the treatment of metastatic brain tumors from esophageal carcinoma.

Methods:

We retrospectively analyzed the clinical characteristics and treatment outcomes in 20 patients with metastatic brain tumors from esophageal carcinoma who underwent SRS at the First Affiliated Hospital, Zhejiang University between July 2011 and February 2015.  

Results:

Twenty patients (24 SRS procedures) of a total of 87 tumors underwent Gammaknife SRS. Tumor histologies were adenocarcinoma in 6 patients (30.0%), squamous cell carcinoma in 14 patients (70%). The median age was 65 years (range 58–73). Eleven patients (55%) presented with multiple metastases (range 2–11), and Nine patients (45%) presented with a single metastasis. The median tumor volume was 0.55 cm3 (range 0.004–44.64 cm3) . No complications related to radiosurgical treatment were identified. The local tumor control rate in this group was 94.2 %. The median marginal dose prescribed was 18 Gy(12–22 Gy). The median survival time from the diagnosis of esophageal cancer was 21.5 months and the median survival from SRS was 16 months. A higher Karnofsky Performance Scale (KPS ) at the time of procedure was associated with an increased survival (p = 0.003). After SRS, four patients had subsequent SRS(one for boost therapy, three for new metastatic deposits), One patient underwent craniotomy due to tumor progression. Of the 19 patients who have died, 17 (89.5%) succumbed to systemic disease progression and 2 (10.5 %) neurologic deaths .  

Conclusion:

SRS is an effective and minimally invasive treatment that can prolong survival. Accordingly, SRS could be used as the initial treatment modality, if possible, even in patients with multiple metastases.

Qingsheng XU (Hangzhou, CHINA), Ying TONG
09:00 - 18:00 #17743 - Stereotactic radiosurgery in 1-5 fractions for brain stem metastases: radiobiologic rationale and logistics informing clinical practice.
Stereotactic radiosurgery in 1-5 fractions for brain stem metastases: radiobiologic rationale and logistics informing clinical practice.

Background: Radiotherapy (RT) is often the definitive treatment for brainstem metastases (BSM), and stereotactic radiosurgery (SRS) offers potential advantages over large volume, conventionally fractionated RT. Achieving intracranial control of BSM without causing symptomatic RT-induced inflammation is key to realizing the clinical utility of SRS. The optimal radiosurgical dose-fractionation with the broadest therapeutic window for BSM is unknown.

Materials/Methods: A retrospective review of brain metastases (BM) treated with single fraction SRS or hypofractionated SRS (HF-SRS) in 2-5 fractions using Novalis Tx or Truebeam STX technology between 2012 and 2016 with planning target volume (PTV) overlap of the brainstem was performed. Simultaneous treatment of other BM and prior BM treatment was permitted. Comparison of continuous variables using Kruskal-Wallis test was performed. The imputed balance of tumor control versus potential toxicity for these cases, based on a simple radiobiologic model, is presented.

Results: 98 courses of SRS/HF-SRS among 87 patients met inclusion criteria. The median age and KPS at SRS/HF-SRS was 62 and 80, respectively. Lung (54%), breast (19%), melanoma (14%), and kidney (7%) were the most common primary tumors. Prior treatments included craniotomy (24%), whole brain RT (30%), and prior SRS/HF-SRS (28%). For the BSM, 42 (43%) and 56 (57%) received SRS and HF-SRS, respectively. The most common technique was volumetric modulated arc therapy with a median of 4 arcs. The number of BM treated simultaneously was higher for SRS than HF-SRS (median 4 vs 2, p<0.01). The BSM PTV was larger for HF-SRS than SRS (median 3.6 vs 0.5cm3, p<0.01). The total PTV of all BM was larger for HF-SRS than SRS (median 8.6 vs 3.1cm3, p<0.01). The prescribed dose/fraction was higher for SRS than HF-SRS (median 15 vs 5 Gy, p<0.01). The prescribed total dose was higher for HF-SRS than SRS (median 25 vs 15 Gy, p<0.01). The maximum brainstem dose was higher for HF-SRS than SRS (median 26.6 vs 12.7 Gy on DVH, p<0.01). There was no difference in overall survival (median 7.4 mo SRS vs 5.8 mo HF-SRS, log-rank p=0.19).

Conclusions: SRS/HF-SRS can conformally treat BSM simultaneously with other BM, acknowledging the sensitivity of this eloquent area to RT-induced toxicity. HF-SRS appears to offer a benefit in broadening the therapeutic window for BSM treatment.

Corbin JACOBS (Durham, NC, USA), Kehali WOLDEMICHAEL, Zhanerke ABISHEVA, Jihad ABDELGADIR, Elizabeth HOWELL, Cosette DECHANT, Scott FLOYD, Jordan TOROK, Justus ADAMSON, Peter FECCI, John KIRKPATRICK
09:00 - 18:00 #17668 - The role of adaptive hypofractionated gamma knife radiosurgery in the acute management of brainstem metastases.
The role of adaptive hypofractionated gamma knife radiosurgery in the acute management of brainstem metastases.

Background:

Intrinsic brainstem metastases are life threatening neoplasms requiring prompt and effective intervention. Microsurgery is often not indicated and systemic treatments are deemed ineffective. In the context of radiation therapy, adverse radiation effects (ARE) remain a major concern. A dose adaptive, image-guided, gamma knife based procedure termed as Rapid Rescue Radiosurgery (RRR) offers the possibility of prompt tumor ablation and sustained local control while reducing the risk of ARE-evolvement. We report the results of RRR applied on a group of patients with this particular type of neoplasm.

Methods:                                                      

8 patients with 9 brainstem metastases, underwent three (3) separate, dose-adapted, MRI-guided, Gamma Knife radiosurgery (GKRS) procedures over 7 days. We performed a retrospective analysis of post-RRR effects which included tumor volume dynamics, local recurrence and ARE-development under the period of treatment and at least 6 months after treatment completion.

Results:

Mean peripheral doses at GKRS 1, GKRS 2 and GKRS 3 were 7.4 Gy, 7.7 Gy and 8.2 Gy (range 6-9 Gy) set at the 35-50% isodose lines. Mean tumor volume reduction was -15% between GKRS 1 and GKRS 3 and -56% at first follow-up (usually 4 weeks after GKRS 3). Mean survival from GKRS 1 was 13 months. 4 patients developed radiological signs of ARE but remained next-to asymptomatic. 2 patients were still alive (10 and 23 months from GKRS 1) at the time of paper submission. 1 patient experienced a local recurrence 34 months after treatment; he died 4 months later of both intra- and extracranial disease. The remaining five cases succumbed to systemic disease progression without neurologic deficit.

 

Conclusions:

In this group of patients, RRR proved effective in the management of brainstem metastases in next-to emergency settings achieving rapid tumor volume decrease, rescue of neurological function, limited ARE and sustained response. Yet, distant failure remains a problem. To optimize RRR-treatments, immune-mediated mechanisms aiming to synergize and expand the effects of radiation to distant sites are necessary.

Georges SINCLAIR, Georges SINCLAIR (Reading, UK, UK), Hamza BENMAKHLOUF , Heather MARTIN, Markus MAEURER, Markus MAEURER, Mustafa Aziz HATIBOGLU, Ernest DODOO, Ernest DODOO, Georges SINCLAIR
09:00 - 18:00 #17670 - The role of adaptive hypofractionated gamma knife radiosurgery in the acute management of fourth ventricle compression due to brain metastases.
The role of adaptive hypofractionated gamma knife radiosurgery in the acute management of fourth ventricle compression due to brain metastases.

 

Background:

20-30% of all intracranial metastases are located in the posterior fossa. The clinical evolution hinges on factors such as tumour growth dynamics, local topographic conditions, performance status and prompt intervention. Fourth ventricle (V4) compression with secondary life-threatening obstructive hydrocephalus remains a major concern, often requiring acute surgical intervention. We have previously reported on the application of adaptive hypofractionated Gamma Knife Radiosurgery in the acute management of critically located metastases, a technique coined by us Rapid Rescue Radiosurgery (RRR). We report the results of RRR in the management of posterior fossa metastases and ensuing V4 decompression.

Case description:

Four (4) patients with V4 compression due to posterior fossa metastases were treated with RRR by means of three (3) separate gamma knife radiosurgical sessions (GKRS) over a period of seven days. Mean V4 volume was 1.02 cm3 at GKRS 1, 1.13 cm3 at GKRS 2 and 1.12 cm3 at GKRS 3. Mean tumor volume during the week of treatment was 10 cm3 at both GKRS 1 and 2, and 9 cm3 at GKRS 3. On average, we achieved a tumor volume reduction of 52% and a V4 size increase of 64% at first follow-up (1 month after treatment completion). Long term follow-up showed continued local tumour control, stable V4 volume and absence of hydrocephalus.

Conclusion:

For this series, RRR was effective in terms of rapid tumour ablation, V4 decompression, and limited toxicity. This surgical procedure may become an additional tool in the management of intractable posterior fossa metastases with underlying V4 compression. More studies involving larger number of patients are warranted.

Georges SINCLAIR, Georges SINCLAIR (Reading, UK, UK), Georges SINCLAIR, Hamza BENMAKHLOUF , Mustafa Aziz HATIBOGLU
09:00 - 18:00 #16702 - Tumor control and survival in patients with ten or more brain metastases treated with stereotactic radiosurgery: a retrospective analysis.
Tumor control and survival in patients with ten or more brain metastases treated with stereotactic radiosurgery: a retrospective analysis.

Object: 
To assess tumor control and survival in patients who were treated with stereotactic radiosurgery (SRS) for 10 or more metastatic brain tumors. 

Methods: 
Patients treated with SRS for 10 or more total brain metastases at this institution between March 2014 and April 2018 were retrospectively identified. Patient records were reviewed for clinical follow-up data, and post-treatment magnetic resonance imaging (MRI) studies were used to assess tumor control. For tumor control studies, patients were separated into two groups: those who received treatment for 10 or more synchronous metastases and those who received several treatments for 10 or more metachronous lesions. Tumor control was then assessed at intervals of three, six, and nine months. Overall survival was calculated from the first SRS treatment date. The Kaplan-Meier method was used to fit survival curves for the data, and log-rank and Cox proportional-hazards regression were employed to analyze the influence of several variables.

Results: 
Fifty-five patients were treated for 10 or more total brain metastases with SRS. On average, patients were treated for a total of 17.5 metastases, with a median of 10 metastases treated per encounter. Forty patients received synchronous treatment, while 15 patients received metachronous treatment. Median overall survival was 10.9 months. Cox proportional-hazards analysis revealed a significant association between patients receiving larger brain volumes irradiated with 12 Gy and decreased overall survival (p=0.0406); however, significance was lost on multivariate analysis. Among patients who received synchronous treatment for 10 or more metastases, the median percentage of tumors controlled was 100%, 91%, and 82% at 3, 6, and 9 months, respectively. Among patients who received metachronous treatment for 10 or more metastases, the median percentage of tumors controlled after each SRS encounter was 100% at all three time points. 

Conclusions: 
SRS can be used to treat patients with 10 or more total brain metastases with an expectation of tumor control and overall survival that is equivalent to that reported for patients with four or fewer tumors. Development of new metastases leading to repeat SRS is not associated with worsened tumor control or survival. Survival may be adversely affected in patients having a higher volume of normal brain irradiated.

Ehrlich MATTHEW (Lake Success, NY, USA), Jonathan KNISELY, Jenghwa CHANG, Xin QIAN, Anuj GOENKA, Elliot SCHUFF, Michael SCHULDER
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EPOSTER - 10 Physics
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17763 - A validation method for SF QA through pinpoint ionization chamber measurement.
A validation method for SF QA through pinpoint ionization chamber measurement.

Introduction: Quality Assurance (QA) is a fundamental stage in radiotherapy treatment (RT), but When it comes to small-field (SF) irradiation, common in Stereotactic Radiation Surgeries (SRS), there is a lack of recommendations. Not until recently, with TRS483 (IEAE, September 2017), there was no document guiding SF-QA in a dosimetric perspective. The services that performed dosimetric QA based their methodology in articles published independently. In Brazil, the scarcity of guidelines is even more evident. Objective: We propose a method to implement dosimetric IF-QA of delivered dose calculated by the Treatment Planning System (TPS) and present cases of validation based on comparison to the CLINAC commissioning tables. Methodology: A cross-calibration was performed between two types of ionization chambers (IC), a referred-laboratory calibrated Farmer IC and a Pinpoint IC, in a standard reference field. The correction factor was obtained. The values for the correction by beam quality for small fields were then determined through the measure of TPR20,10 for different sizes of irradiation fields. After that, six SRS plans were reviewed, with treatment fields irradiating the Pinpoint CI. Readings were adjusted by the obtained KQ factors depending on TPR20,10, and the corrections of influence quantities were considered. Results: The values of TPR20,10 are coherent with those presented on TRS483, with a maximum difference of 2,5% for an irradiation field 4x4cm2. Among the reviewed treatment plans, the difference between the dose calculated by the TPS and the measured dose corrected by the factors varied from -2,7% to 1,3%. Discussion: The proposed methodology resulted in close values of estimated dose by the TPS and dose measured by the Pinpoint CI. The data of TPR20,10 and dose for small fields should be verified by Monte Carlo simulations for a more reliable validation. Conclusion: The proposed methodology is feasible, improving SRS treatment security through more reliable SF-QA.

André EZEQUIEL LÔBO DE ABREU, Tiago BATISTA OLIVERA (Ipatinga/MG, BRAZIL), Gerson Hiroshi YOSHINARI JR., Mariana PARANHOS ALVARENGA, Harley FRANCISCO DE OLIVEIRA
09:00 - 18:00 #17832 - Assessment of difference in dose volume histogram bin calculation for the new version of gamma knife treatment software.
Assessment of difference in dose volume histogram bin calculation for the new version of gamma knife treatment software.

Introduction: In the latest Gamma Knife planning software, Gamma Plan (GP) version 11.1.1, dose volume histograms (DVH) are now binned in 0.1 % at the measurements window compared to 0.5 % as it was before on the previous versions. The effect of this improved calculation can potentially change the prescription dose method especially for centers like ours where the 100% prescription coverage was usually defined using DVH from the measurement window. In this study we compared plans with 99.5 % coverage versus 99.95% coverage using the measurement window. The difference may not look large but it may potentially affect our goal for coverage in order to standardize our planning.

 

Methods: A total of 20 clinically used plans were created with 99.5% and 99.95% coverage by adjusting only the prescribed isodose lines (IDL) which was our standard clinical practice to achieve 100% coverage. Difference between both types of plans were evaluated using dosimetric treatment parameters as a voxel minimum dose, voxel maximum dose, maximum dose of 0.035 cm3 target volume dose, and a mean target dose.  The treatment plans differences in selectivity and gradient indexes were also studied.

 

Results: The increase for a voxel minimum dose, voxel maximum dose, maximum of 0.035 cm3 target volume dose and a mean target dose were in the range of 3 – 6% for 99.95 % coverage of the target compared with 99.5% of coverage.  As a result, by trying to cover an additional 0.45% of the target, we are effectively increasing the dose to the target for the same prescription. For instance, 15 Gy with 99.95% coverage could be more like 16 Gy with 99.5% coverage in terms of similar minimum, maximum and mean doses. Selectivity for the plans with 99.95% coverage decreased, but the gradient index improved.

 

Conclusion: The coverage goal will need to account for the difference in how DVHs are displayed in with the new GP update. This change may result in a clinically significant dose adjustment and needs to be considered for clinical implications and comparison with treatments delivered using old versions of GP.

Gennady NEYMAN (Cleveland, USA), Peng QI, Jennifer YU, Erin MURPHY, Gene BARNETT, John SUH, Samuel CHAO
09:00 - 18:00 #17563 - CBCT-guided cranial radiosurgery validation process by end-to-end test with TLD and film in a SRS head phantom.
CBCT-guided cranial radiosurgery validation process by end-to-end test with TLD and film in a SRS head phantom.

Purpose: The main purpose of this work was to show the availability of perform a frameless cone-beam computed tomography (CBCT)-guided cranial stereotatic radiosurgery (SRS) by an end-to-end (E2E) test with IROC Houston SRS head phantom using the Varian Clinac iX.

Methods and Materials: The head phantom has two inserts, one for the imaging containing the target and the dosimetry insert with film and thermoluminescent dosimeter (TLD). The imaging insert has a nylon sphere embedded in water as the target volume (simulating the tumor). The dosimetry insert contains two orthogonal sheets of Gafchromic passing throug the center of the "tumor" and two TLD within 0.5cm of the center of the target. The phantom with both inserts was imaged with computed tomography (CT) and magnetic resonance imaging (MRI), and a SRS dynamic arc plan was generated to the one with the imaging insert. The purpose of the plan was to cover the target with 25Gy with the prescription isodose being more than 85%. The phantom was localized at the treatment table with CBCT and the imaging insert was changed to the dosimetry one to be irradiated. Comparisons of the planned and the delivered dose to the film and TLD were performed. For the film, the coronal and sagital sheets were analysed with the gamma index with of difference dose 5% and distance-to-agreement (DTA) of 3mm with minimum of 85% of the points meeting the criteria. For the TLD the dose to the center of the target was compared with the plan and must meet the criteria of 95% to 105% of the read dose.

Results: The dosimetric results met the porposed criteria. The gamma index of the of both film sheets (coronal and sagital) agreed with the gamma index in 96% of points. The ratio of the dose to the center of the TLD and of the plan was 0.98.

Conclusions: The end-to-end test procedure proposed by to evaluate the abilities to locate and treat an intracranial target with high precision was performed with success in a frameless setup and CBCT method for positioning.

Anderson MELO (Maceió, BRAZIL), Landobergue BARROS
09:00 - 18:00 #17845 - Clinical implementation of a dedicated brain treatment planning optimizer for stereotactic treatments.
Clinical implementation of a dedicated brain treatment planning optimizer for stereotactic treatments.

Purpose:

Clinical implementation of a novel dedicated and automated treatment-planning solution for cranial indications, Elements. Single lesions can be targeted with an inversely optimized VMAT approach using automated arc trajectory optimization (Cranial SRS Element, Brainlab, München, Gernmany) while up to fifteen metastastic brain tumors can be automatically targeted with a single isocenter and multiple inversely-optimized dynamic conformal arcs (Multiple Brain Mets SRS Element, Brainlab, München, Gernmany).

Material and Methods:

The very first 25 treated patients were analyzed, each representing a variable number of lesions (1-12). Depending on the number and location of the lesions a dedicated Element was selected and used in order to achieve the specific planning constraints.The plans were evaluated by means of Paddick conformity (CI) and gradient index (GI). Patient specific quality assurance (QA) was performed with gafchromic EBT3 film and portal imager.

Results:

The Elements software tools generated plans with CI of 0.71±0.09 and a gradient index of 3.9±1.4. All plans achieved the organ at risk constraints. A gamma of 3%/3mm was used for the QA. A 98 % and 98,2 % passing rate was found for the EBT3 film and portal imager, respectively. This shows also the good concordance between film and EPID, suggesting that patient specific QA can be performed with the portal imager rather than the time-consuming films.

Conclusions:

The automated dose planning Elements revive dynamic conformal arcs as the paradigm for linac-based stereotactic radiosurgery of multiple brain metastases and at the same time implements an improved VMAT approach for single lesions with the use of automated arc trajectory optimization. This study shows the implementation of this technique in the routine clinical environment with an improved planning and treatment efficiency.

Thierry GEVAERT (Brussels, BELGIUM), Andrea GIRARDI, Benedikt ENGELS, Marlies BOUSSAER, Chaïmae EL AISATI, Mark DE RIDDER
09:00 - 18:00 #17897 - Commissioning and end-to-end validation for a high dose rate beam for radiosurgery.
Commissioning and end-to-end validation for a high dose rate beam for radiosurgery.

Currently, stereotactic radiosurgery and hypofractionated treatments become increasingly frequent, being the source of many studies. Associated with the new definitions and adjustments for small fields, the commissioning and validation of a high dose rate beam for small field treatments requires an adjustment to the factors suggested by the new IAEA document which infers factors for correction of the readings made by the detectors in the small field situations. A 6MV beam with high dose rate was commissioned and validated for Eclipse, with the AAA algorithm using the blue phantom, a PTW 3D pinpoint ionization chamber and an unshielded diode for the small fields. Following the protocol methodology, the 5x5 field was used as the fmsr field. Thus, the dose profiles: depth dose, inplane and crossplane of the beams were acquired with the two detectors for the square fields of 5 cm to 1 cm to identify the effects suggested by the literature. The output factor was acquired for all symmetrical and asymmetric field sizes with the pin point camera and, with the diode, for the fields equal to and less than 5 cm. Data were treated as recommended by the literature, including current work, and were fed into the planning system. The validation was done initially with a uniform phantom of solid water and already showed good agreement of the field factors and simplified plans, with discrepancies less than or equal to 1%. In an anthropomorphic phantom STEEV by cirs were simulated radiosurgery treatments with non-coplanar 3D and VMAT fields, both showed maximum discrepancies in approximately 1%.

Thiago B SILVEIRA, Maira R SANTOS (Rio de Janeiro, BRAZIL), Mozart G DUARTE
09:00 - 18:00 #17736 - Comparison between volumetric modulated arc therapy and dynamic conformal arc stereotactic radiotherapy for intracranial lesions.
Comparison between volumetric modulated arc therapy and dynamic conformal arc stereotactic radiotherapy for intracranial lesions.

The purpose of this study is to evaluate the dosimetric differences between treatment plans using dynamic conformal arc therapy (DCAT) from two TPS’s (Varian Eclipse and Brainlab elements) and volumetric modulated arc therapy (VMAT) from Varian Eclipse TPS, via frameless, linear accelerator based stereotactic radiotherapy (SRT) for the treatment of brain lesions for the first use of stereotactic radiotherapy in Algeria Using a Varian iX23 Linear Accelerator, Brainlab's 6D Exactrac Positioning System and Robotics couche, and TPS’s Elements (Brainlab) and Eclipse (Varian). Three plans were developed per each patient, with a total of fifteen patients, utilizing DCAT and VMAT. The plan comparisons of 45 treatment plans include the target coverage, conformity index (CI), homogeneity index (HI), gradient index (GI), and the volume of the normal brain tissue receiving doses of 12 and 5 Gray (Gy). Results of this research outline which planning method may provide benefits or lack thereof depending on the brain lesion location and size, thus providing data in terms of conformity of target coverage as well as lower dose spillage to the rest of the brain. This study also provides dosimetric results regarding advantages and disadvantages of forward versus inverse planning, in addition to the impact of a multi-leaf collimator (MLC) width size. Potentially the results of the study will indicate the most beneficial technique for delivery of SRS treatments for intracranial tumors.

Samir BENCHEIKH, Malika BESBAS, Ryma LOUELH, Mourad BELMESSAOUD, Abdelkader TOUTAOUI (Tizi Ouzou, ALGERIA)
09:00 - 18:00 #17726 - Contribution of scattered radiation to image formation and imaging dose in CyberKnife radiosurgery.
Contribution of scattered radiation to image formation and imaging dose in CyberKnife radiosurgery.

Purpose: Evaluate the contribution of scattered radiation to radiographic image formation and perform calculations of the imaging dose delivered by the x-ray based image guidance system of a CyberKnife radiosurgery system.

Methods: The CyberKnife image guidance subsystem consisting of two x-ray tubes and two flat panel detectors situated at the ceiling and the floor of the treatment room, respectively, were modeled and used to perform Monte Carlo (MC) simulations for water phantoms of different radii centered at the isocenter, as well as, for intracranial radiosurgery cases. Patient head models were simulated using lattice geometries constructed on the basis of information retrieved from corresponding CT scans. The MCNP6 general purpose MC code was employed to simulate photon transport and score i) the fluence of phantom/patient-scattered photons incident on the image detectors and ii) the imaging dose delivered for different kVp settings.

Results: The contribution of scattered radiation incident on the detector was found to depend on the dimensions of the imaging object and the kVp setting,reaching up to 30% at the center of the detectors for the 30cm diameter phantom and 150kVp. An imaging dose of 0.4mGy for the eye lenses and less than 0.1mGy for the healthy brain was calculated for an image acquisition using both tubes and typical settings of 120kVp and 10mAs.

Conclusions: The scatter contribution in radiographic image of a CyberKnife system is decreased due to the increased distance of 140cm between the patient and each detector. An imaging dose per acquisition of 0.4mGy was found for the eye lenses which corresponds to 4cGy for a treatment using a typical number of 100 acquisitions. Further studies to model the contribution of scattered radiation and improve low contrast resolution which is of interest in extracranial radiosurgery will be performed. 

Panagiotis ARCHONTAKIS, Argyris MOUTSATSOS, Emmanouil ZOROS (Greece, GREECE), Eleftherios PAPPAS, Evaggelos PANTELIS
09:00 - 18:00 #17788 - Development of a stereotactic system as a basic concept for diagnostic biopsy as well as lesioning or stimulation of relevant brain structures.
Development of a stereotactic system as a basic concept for diagnostic biopsy as well as lesioning or stimulation of relevant brain structures.

Currently, complex stereotactic systems are used to act in the brain as three-dimensional organ. The biggest barrier of these systems available to date is their high investment requirements (up to 150 TEURO), their enormous weight (up to 5000 g) and their very complex assembly, including the long learning curve.

The aim is to develop a safe and simple stereotactic system that guarantees the same or better precision as traditional systems, but greatly simplifies acquisition and handling.

We developed a system based on a patient-specific 3D platform, which contains a total weight of 300 g. This platform contains all relevant information of the target and entry point and allows a tenth of a millimeter placement of biopsy needle or functional equipment. First, three, max. four small bone screws (frontal/parietal) fixed in the cranial bone followed by the acquisition of a CT or MR dataset. With the planning data, we construct a virtual platform for placement of the desired instruments. This model is 3D printed and attached to the re-exposed bone screws during surgery. This offers the option of a bi-hemispheric operation and helps to reduce the cost per patient by up to 40% of the conventional price.

An initial accuracy study (n = 40) documents a precision of the instrument tip (biopsy needle) of 0.58 mm ± 0.34 mm (ranging from 0.09 mm to 1.17 mm), comparing the target performance based on CT data of planned to actual instruments tip.

The system developed in Germany represents an excellent alternative to traditional stereotactic systems and helps to establish stereotaxy as a routine procedure. Furthermore, these platforms are single use as well as individual for each patient. The implementation of all spatial coordinates in the design of the platform eliminates intraoperatively all adjustment processes and shortens the duration of surgery by up 30%.

Juan Carlos CAMACHO RODRÍGUEZ, Dirk WINKLER (, GERMANY), Christian FIEDLER, Robert MOEBIUS, Marcel MULLER, Ronny GRUNERT
09:00 - 18:00 #17795 - Evaluation of the Explorer 4D treatment planning system.
Evaluation of the Explorer 4D treatment planning system.

Objectives: The ARI GammaART 6000ND rotating gamma systemwas installed in August 2007 at the University of Debrecen and has been used to treat more than 4500 patients since then. Regular tests are performed by the medical physics group following stringent quality assurance guidelines.The objective of this paper is the assessment of the Explorer 4DTM  treatment planning system (TPS).

Methods:  GAFchromicTMEBT 3 films were used to verify the 50% isodose lines of the TPS. The films were irradiated in a water equivalent phantom and then evaluated with FilmQATMPro software. The actual results were compared with the 50% isodose lines of the TPS. A PTW pinpoint 3D ionization chamber was placed inside a water equivalent phantom to verify the output factors built into the TPS.

Results: Statistical analysis of the results show that the difference between the 50% isodose lines of the TPS and the actual irradiation was maximum 2.35%.  In regards to the output factors, the results show less than 1% deviation from the TPS, except for the 4mm collimator, where the measurements were not reliable.

Conclusions: The results show that the TPS performs within the required tolerances to perform stereotactic treatment planning for intracranial indications.

Tamás HOLLÓ, Gulyás LÁSZLÓ (Debrecen, HUNGARY), László BOGNÁR, Imre FEDORCSÁK, József Gábor DOBAI
09:00 - 18:00 #16810 - Four-dimensional digital tomosynthesis based on visual respiratory guidance.
Four-dimensional digital tomosynthesis based on visual respiratory guidance.

The aim of this research was to introduce and evaluate a respiratory-guided slow gantry rotation 4D digital tomosynthesis (DTS). For each of 10 volunteers, 2 breathing patterns were obtained for 3 minutes, one under free breathing condition and the other with visual respiratory-guidance using an in-house developed respiratory monitoring system based on pressure sensing. Visual guidance was performed using a 4s cycle sine wave with an amplitude corresponding to the average of end-inhalation peaks and end-exhalation valleys from the free-breathing pattern. The scan range was 40 degrees for each simulation, and the frame rate (FR) and gantry rotation speed (GRS) were determined so that one projection per phase should be included. Both acquisition time (AT) and the number of total projections to be acquired (NPA) were calculated. Applying the obtained respiration pattern and the corresponding sequence, virtual projections were acquired under a typical geometry of Varian on-board imager for two virtual phantoms, modified Shepp-Logan (mSL) and XCAT (extended Cardiac-Torso). For the XCAT, two different orientations were considered, anterior-posterior (i.e., coronal) and left-right (i.e., sagittal). Projections were sorted to 10 phases and image reconstruction was made using a modified filtered back-projection. Reconstructed images were compared with the planned breathing data (i.e., ideal situation) by SSIM (Structural Similarity) and NRMSE (Normalized Root-mean-square Error). For each case, simulation with guidance (SwG) showed motion-related artifact reduction compared to that under free-breathing (SuFB). SwG required less NPA but provided slightly higher SSIM and lower NRMSE values in all phantom images than SuFB did. In addition, the distribution of projections per phase was more regular in SwG. Through the proposed respiratory-guided 4D DTS, it is possible to reduce imaging dose while improving image quality.

Kim DONG-SU, Kim SIYONG, Suh TAE SUK (Seoul, KOREA)
09:00 - 18:00 #17719 - Frame-based to frameless brain SRS. Single centre experience in short time technological evolution.
Frame-based to frameless brain SRS. Single centre experience in short time technological evolution.

Mevaterapia medical centre put together a multidisciplinary team to implement frame-based brain SRS using a VARIAN Trilogy LINAC early 2017. Over 2 years a continuous technology upgrade has been performed in order to being able to perform safe frameless brain SRS.

First patient was treated during June 2017, with two treatment workflow considered; single fraction patients with stereotactic frame or hypofractionated patients with BrainLab stereotactic mask. Patient localization was performed based on CBCT imaging using a tolerance criteria 1mm/1°, achieving 6 degree positioning combining Varian couch with couch-mount movements.

During November 2017 ExacTrack imaging system was integrated to our LINAC, and imaging localization transition was carried out from CBCT to ExacTrac based imaging over 2 month. Positioning tolerance criteria was kept 1mm/1°.

In May 2018, we upgrade our treatment couch to BrainLab robotic 6D couch allowing ourselves to perform frameless SRS treatments. Frame-based to Frameless workflow was carried out progressively over 4 month with selected patients in joint decision between radiation oncologist and neurosurgeons. Multiple brain metastasis SRS was incorporated to our clinical protocol and positioning tolerance was set to 0.5mm/0.5°.

In room treatment time over our technological evolution was assessed and compared, considering that positioning tolerance was kept over these 2 years and more than 100 patients. CBCT imaging based treatments were performed in 60±20 minutes, when ExacTrac was implemented with Varian couch total time reduced to 40±10 minutes. Finally, actual in room treatment time with Frameless technology using ExacTrac plus robotic 6D couch is reduced to 30±10 minutes. Total patient time in treatment was reduced in over 40% with equivalent treatment quality and a quantitative increase in patient comfortability.

Florencia MAURI, Leon ALDROVANDI, Ruben Oscar FARIAS, Augusto ALVA, Pablo Marcelo AJLER, Matteo BACCANELLI, Federico Javier DIAZ, Maria Liliana MAIRAL, Claudio Gustavo YAMPOLSKY, Mabel Edith SARDI, Mara Lia SCARABINO (Buenos Aires, ARGENTINA)
09:00 - 18:00 #17566 - Geant4-based Monte Carlo simulation of correction factors for reference dosimetry of the Leksell Gamma Knife Perfexion.
Geant4-based Monte Carlo simulation of correction factors for reference dosimetry of the Leksell Gamma Knife Perfexion.

With the publication of TRS-483 in late 2017 the IAEA has established an international Code of Practice (COP) for reference dosimetry in small and non-standard fields based on a formalism first suggested by Alfonso et al. in 2008. However, data on correction factors for the Leksell Gamma Knife Perfexion is scarce and what little data is available was obtained under conditions not necessarily in accordance with the IAEA’s recommendations. This study constitutes the first systematic attempt to calculate those correction factors by applying the new COP to Monte Carlo simulation using the GEANT4 toolkit. The correction factors were determined for three common ionization chamber detectors, modeled in great detail based on proprietary blueprints provided by their respective manufacturers, in five different phantom materials and using three different physics lists. The results indicated that for chambers with a collector electrode made of low-Z materials, correction factors were within 1% of unity for the liquid water, Solid Water™ and polystyrene phantom materials, whereas chambers with a collector electrode made of heavier elements and electronically denser phantom materials necessitated larger corrections. The correction factors did not differ significantly between the various physics lists. Similarities and differences between the results of this study and previous ones based on EGSnrc and PENELOPE-based Monte Carlo codes were also analyzed and it was found that the results obtained herein were generally in good agreement with the findings of earlier studies that were obtained under comparable reference conditions. The correction factors obtained in this study can be a contribution to a potential revision or update of TRS-483.

Thomas SCHAARSCHMIDT, Tae-Hoon KIM, Young Kyun KIM, Hye Jeong YANG, Kook Jin CHUN, Eun Young KIM, Hyun-Tai CHUNG (Seoul, KOREA)
09:00 - 18:00 #17890 - Hypofractionated treatments using Gamma Knife Icon: accuracy evaluation of the daily repositioning.
Hypofractionated treatments using Gamma Knife Icon: accuracy evaluation of the daily repositioning.

The major improvement of Gamma Knife Icon is the possibility to execute frameless treatments to treat large-volume lesions or lesions close to critical organs reducing the side effects to normal tissues.

A possible issue using the frameless modality for hypofractionated treatments is the accuracy and reproducibility of the patient positioning. 

The patient displacement measurements (rotation and translation along the x/y/z axis) have been collected for each fraction and then the data have been analyzed to verify the accuracy and the efficiency of the current positioning procedure.

Between October 2017 and January 2019, 417 patients were treated in Fondazione Poliambulanza, including 65 in frameless mode with the thermoplastic mask, in single or multi-session fractions. In the first 57 hypofractionated treatments (3,4,5 days, for a total of 256 fractions) we studied the error (offset) in the daily repositioning of the patient in the three X-axis, Y, Z both for rotation and for translation. We obtained the following results (the value can be positive or negative depending on the side from which the new positioning moves with respect to the first day): 

- X rotation: mean -0.10°, SD 0.62°; 

- Y rotation: mean 0.08°, SD.53°; 

- Z rotation: mean 0.05°, SD 0.40°; 

- Translation X: mean -0.02 mm, SD 0.25 mm; 

- Translation Y: mean -0.28 mm, SD 0.22 mm; 

- Translation Z: mean -0.04 mm, SD 0.99 mm. 

The most frequent error in translations was found within 0.5 mm; in rotations, within 1°. In translations, the axis most frequently involved is the Y axis (antero-posterior), while the higher error, although less frequent, occurs above all on the Z axis (head-feet). For the rotations, the statistic did not show a preferential axis between X, Y or Z. Overall, the fixing system consisting of the thermoplastic mask and the customized conformable pillow was reliable, easy to use for the operator and was well tolerated by all the treated patients.

Alberto FRANZIN (Brescia, ITALY), Chiara BASSETTI, Lodoviga GIUDICE, Cesare GIORGI, Ivan VILLA, Marco GALELLI, Oscar VIVALDI, Mario BIGNARDI
09:00 - 18:00 #17880 - Image processing for radiosurgery using computer deep learning.
Image processing for radiosurgery using computer deep learning.

In radiosurgical operations, the accuracy of planning and drawing of target structures as well as the definition of risk structures is very important.

The planning of the radiosurgery is performed mainly by CT and MRI images, which are transferred after they are merged into the virtual planning system. Visualization and virtual planning greatly assist the subjectivity of hand drawing contour of brain structures by the neurosurgeon for optimization of treatment.

The new proposed system allows to search quickly for the very large amount of information needed to better diagnose and design a further treatment that help the physician in the decision-making algorithm and provide better treatment outcomes for radiosurgery. Priority is given to the processing of image information from CT, MRI and PET considering the different quality of the devices, which is reflected in the different sensitivity and specificity of the results obtained by imaging and clinical methods. This information, if necessary, are displayed in 3D stereoscopy. The processing of sophisticated information system methods by combining the results of multiple imaging (CT, MRI, PET) increase the specificity and sensitivity of the algorithm of interpretation and decision making for the diagnosis and treatment of the patient, which is also a shift towards personalization for the decision algorithm. This system allows through the secure network to communicate between hospitals to diagnose correctly and thus decide the treatment method correctly. At the same time, the system is designed to have the ability to communicate with existing PACS systems in hospitals and "self-deep learning" skills.

Visualization and communication across the hospital network will enable you to prepare radiosurgery with experts from different hospitals, thus increasing the emphasis on the accuracy of the planning process.

Miron ŠRAMKA, Eugen RUŽICKÝ (Bratislava, SLOVAKIA), Alena FURDOVÁ, Štefan KOZÁK, Ján LACKO
09:00 - 18:00 #17842 - Impact of patient-specific MRI distortion correction for stereotactic cranial target definition.
Impact of patient-specific MRI distortion correction for stereotactic cranial target definition.

Introduction

The accuracy of a stereotactic treatment is primarily limited by the least accurate process in the whole chain of events from patient scanning to patient treatment.

The targeting is limited by the accuracy of the CT and MRI images. MRI datasets are subjected to distortions, due to nonlinearity of gradient fields, andmay cause incorrect target definition.

This study aimed to analyze the impact of a patient-specific algorithm, Crainial distortion Elements (Brainlab, München, Germany), rather than a manufacture-specific, to correct spatial distortion in cranial magnetic resonance images.

Methods and materials

Twelve trigeminal patients treated with a single dose of 90 Gy with a 4mm collimator were studied retrospectively.  The gross target volume (GTV) was defined on a 1.0mm T1 MPRAGE and T2 MRI corrected for distortion with a machine-specific algorithm.

For this study, the manufacture-specific corrected MRI was further corrected using a patient-specific distortion correction algorithm that references the treatment planning CT. The GTV were then mapped onto this newly created patient specific corrected MRI dataset.

The original defined target and the corrected deformed object were mutually compared by means of several quantitative measures such as Dice, Jaccard, and Hausdorff indices. The average distance between the two centers of the two GTV was also calculated.

 

Results

On average, a good agreement was found between both GTV resulting in a Dice index of 0.76 (SD 0.23) ranging between 0.13 and 0.92. The Jaccard index, which is an intersection over Union was similar (p> 0.1) to the Dice with an average of 0.66 (SD 0.23) ranging between 0.09 and 0.86. The greatest of all the distances from a point in GTV to the closest point in the other GTV, called the Hausdorff distance, was 0.73 on average (range 0.50-1.80), reflecting good similarity between both GTVs.Average distance between both GTV was 0.43 mm (SD0.26mm), with a minimum of 0.20 mm and a maximum of 1.10 mm. One out of the 12 patients met criteria of “geometric miss”, which was not correlated with clinical outcome.

 

Conclusion

Our study showed that the cranial distortion Elements correct all images even when manufacture-specific corrections fail due to patient specific conditions. In order to avoid any geometrical miss, a patient specific distortion correction must be applied for all cranial indication.

Thierry GEVAERT (Brussels, BELGIUM), Benedikt ENGELS, Chaïmae EL AISATI, Mark DE RIDDER
09:00 - 18:00 #17751 - Implementation of a national stereotactic radiosurgery chart round: engagement and clinically significant outcomes.
Implementation of a national stereotactic radiosurgery chart round: engagement and clinically significant outcomes.

Introduction

Intracranial and extracranial Stereotactic Radiosurgery (SRS) are highly specialised techniques which require careful and structured implementation.  Here we describe the implementation of a weekly national SRS chart round attended by specialists from 10 geographical locations, held via videoconference. Prior to SRS delivery, all patients had their case presented where clinical, planning and technical details were discussed.

 

Method

Data was collected from weekly run chart rounds between July 2018 and January 2019.  Details recorded included specialty attendances, clinical background, diagnosis, volumes, radiation dose and fractionation, treatment site/location and clinician approach.  Furthermore, consensus recommendations regarding changes to treatment approaches were also recorded.

 

Results

There were 590 attendances split across radiation therapists/dosimetrists (29.0%), radiation medical physicists (27.6%), oncologists (27.3%) and management (16.1%).  There were 118 cases presented. Of these, primary or oligometastatic lung malignancies represented the majority of cases (n=42), followed by brain metastases (n=21 and n=14 for single met and multi-met respectively), bony oligometastases (n=17), non-bone oligometastases (n=11), spine (n=3), benign brain conditions (n=3) and primary brain (n=1).  Across our national network we have had 18 radiation oncologists present at least one case at the chart round with others participating for training and mentorship.  Of the 118 cases presented, there were 29 (24.6%) recommendations made for 21 patients.  These included changes to contours (n=10), dosimetry (n=4), treatment technique (n=1) dose/prescription (n=8) and 6 occasions where standard fractionation or no treatment was recommended.  Three patients had more than one recommendation made.  Cases were re-presented following changes from recommendations.  

 

Conclusion

The implementation of a national SRS chart round, held via videoconference has ensured national protocol compliance to stereotactic treatments across our network.  Furthermore, the chart rounds have allowed clinicians to be provided with mentorship and guidance from nationally and internationally recognised SRS experts which has allowed for increased plan quality and patient outcomes.

Rhys FITZGERALD (Brisbane, AUSTRALIA), Trent ALAND, David PRYOR, Lee ANDERSON, Andrew FONG, Dominic LUNN, Andrew OAR, Marcel KNESL, Jim JACKSON, Matthew FOOTE
09:00 - 18:00 #17710 - Implementation of a novel non-coplanar arcs technique for stereotactic treatment of brain metastases.
Implementation of a novel non-coplanar arcs technique for stereotactic treatment of brain metastases.

Purpose: Implementation of stereotactic radiosurgery (SRS) treatment for brain metastases in our department with no previous SRS experience, using the dedicated technique HyperArc™, Varian Inc. (HA) on a TrueBeam STx.

Material and Methods: The accuracy of the HA patient positioning system, MV and Cone-Beam computed tomography (CBCT) in conjunction with the 6D robotic couch were evaluated. Brainlab ExacTrac (ET) was used to verify patient positioning prior to each beam and trigger new CBCT correction. Dedicated beam models for millennium and HD multi leaf collimator (MLC) were commissioned. Coincidence of imaging and radiation isocenters was confirmed using Winston-Lutz (WL) test. EBT3 film measurements were done for Picket Fence (PF) test, end-to-end (EE) test using a Max HD phantom and clinical pre-treatment Quality-Control (QC) using a CIRS phantom. The first 21 patients (1-4 brain metastases) have been treated using 4 non-coplanar 180°-arcs in one fraction of 18Gy. A 2 mm margin was applied to the gross target volume delineated on magnetic resonance images. Plans were evaluated with dosimetric indices, total monitor units and overall treatment time (OTT) per fraction.

Results: The CBCT and ET isocenters agreed to within 0.4 mm and 0.3° in translational and rotational directions. The beam models were accurate down to a jaw field of 2 x 2 cm2 with dosimetric leaf gaps of 0.15 cm and 0.09 cm and transmission factors of 1.8% and 1.2% for 6 MV flattening filter free photon beam with the millennium and HD MLC, respectively. The results of WL (max delta <0.7mm), PF and EE (gamma passing rate >95%) tests were within the defined criteria. The mean Planning Target Volume was 3.3 cm3 (range 0.3-16 cm3). Dose constraints were within tolerances for all the patients. Pre-treatment QC resulted in a local gamma passing rate (1mm/5%) above 90% for all the patients. Maximum observed deviation in patient positioning was 3.2mm/2.4°, 11 patients were within treatment tolerance (1mm/1°) throughout treatment. The mean OTT was 33.5 ± 13.5 min.

Conclusion: HA offers fast accurate treatment planning and dose delivery. By omitting MV images, OTT can be decreased by almost half. Next steps are to investigate the possibility of using only the initial CBCT as image verification, and possible benefits of using HD MLC.

Lucie CALMELS (Herlev, DENMARK), Susan BLAK NYRUP BIANCARDO, David MC KENZIE GRANT, Maria SJÖLIN, Eva WILKEN, Sune Kristian BUHL, Ulf BJELKENGREN, Mette ANDERSEN, Patrik SIBOLT, Mette PEDERSEN, Hanne LANDGREN, Susanne LIND, Anja NIELSEN, Poul GEERTSEN, David SJÖSTRÖM
09:00 - 18:00 #17722 - Initial experience using a bolus skin-equivalent for calvarial metastases and skull defects using the Leksell Gamma Knife ICON mask based system: The Cleveland Clinic Experience.
Initial experience using a bolus skin-equivalent for calvarial metastases and skull defects using the Leksell Gamma Knife ICON mask based system: The Cleveland Clinic Experience.

Introduction: Our group has previously published on the use of a bolus skin-equivalent layer for treating calvarial and skull base metastases using the Perfexion frame based system (Kotecha et al J NSG (Suppl 2) 121:91-101, 2014). Traditionally used TMR 10 algorithms in Gamma Knife Radiosurgery (GKRS) are not accurate in the first 5 mm from the surface and by adding at least 5 mm of bolus material to the mask and creating an extended skull contour that limitation is removed.

Method: We used a bolus skin-equivalent attached directly to the Leksell Gamma Knife ICON thermoplastic mesh faced mask. The system uses image-guidance utilizing cone-beam CT (CBCT) and infrared tracking to ensure minimal inter- and intra-fractional movement during GKRS and hence can also be used in a fractionated manner. Four patients to date have been treated. The thermoplastic mask system consisted of a customized resin-filled neck rest and a 3-point thermoplastic mask. The area to be treated was outlined on the skin so the correct size of bolus would be utilized. A bolus skin-equivalent of at least 5 mm was positioned over the treatment site and attached directly to the thermoplastic mask to artificially extend the surface to target distance. A localization CBCT was completed after the mask was made and the patients then completed high resolution (1 mm slice) contrasted enhanced MRI images and CT scans without and coregistered to reduce inaccuracies from image distortion.

Results: The four cases treated included a 14 year old (y/o) with osteosarcoma skull metastases treated over 3 fractions, a 69 y/o with renal cancer skull metastases treated over 5 fractions, an 81 y/o with atypical meningioma and skull defect treated over 5 fractions, and a 55 y/o with an anaplastic oligodendroglioma and a skull defect treated in a single fraction. The four cases will be presented in detail outlining the treatment flow. We were able to calculate the skin max point dose (Gy) for 3 patients with all falling below the skin tissue constraints using the Timmerman Tables. There was associated hair loss but no skin dermatitis.

Conclusion: Gamma Knife using the ICON mask based system and a bolus allows treatment of superficial calvarial lesions and patients with superficial tumors and skull defects and provides an option for patients who are not candidates for a frame based Gamma Knife procedure.

Glen STEVENS (Cleveland, USA), Lilyana ANGELOV, Sam CHAO, Gennady NEYMAN, Erin MURPHY, Dani FLAK, John SUH
09:00 - 18:00 #17672 - Integrating navigated Transcranial Magnetic Stimulation (n-TMS) in gamma knife radiosurgery planning.
Integrating navigated Transcranial Magnetic Stimulation (n-TMS) in gamma knife radiosurgery planning.

Background:

To illustrate how navigated transcranial magnetic simulation (n-TMS) can be utilized in the radiosurgical management of brain metastases involving areas of the motor cortex.

Case Descriptions:

Case 1: A 53 year-old woman with metastatic breast cancer developed focal epileptic seizures and weakness in her left hand.  A magnetic resonance imaging (MRI) scan demonstrated a partially cystic 30 mm metastasis in the right precentral gyrus and central sulcus. The lesion was treated with adaptive hypofractionated gamma knife radiosurgery; nTMS - based motor mapping was performed prior to treatment. Follow-up MRI up to 12 months revealed a significant decrease in tumor size without adverse radiation effects (ARE); symptoms resolved within one month post treatment.

Case 2: A 73-year-old man with metastatic lung cancer developed left hand weakness. The corresponding MRI demonstrated a 26 mm metastasis in the right postcentral gyrus and sulcus, 5 mm from the hand motor cortex. The patient underwent preoperative nTMS  motor mapping  prior to single dose gamma knife radiosurgery for both lesions. Follow-up MRI examinations up to 10 months showed tumor control and evolving ARE. Despite the latter, the patient experienced motor function improvement  during follow-up.

Conclusion: 

In our case series, nTMS was safely and effectively integrated in gamma knife radiosurgery (GKRS) planning. Motor mapping allowed sparing of healthy functional tissue. The relation between the type of radiation schedule and possible radiation-induced focal plastic distortions at long term needs consideration and deeper analysis.  Prospective studies involving larger, homogenous group of patients are warranted to further validate the clinical significance of nTMS in GKRS-treatment planning. 

Georges SINCLAIR, Georges SINCLAIR (Reading, UK, UK), Georges SINCLAIR, Gerald COORAY, Hamza BENMAKHLOUF , Christer LINDQUIST, Mominul ISLAM
09:00 - 18:00 #17811 - Monte Carlo evaluation of the effect of source self-shielding on Gamma Knife dose rate variation.
Monte Carlo evaluation of the effect of source self-shielding on Gamma Knife dose rate variation.

In this work, we analyze the effects of source self-attenuation on the dose rate for a Model C Gamma Knife unit (Elekta, Stockholm. As each source is composed of 20, 1 mm thick individual pellets and the source housing necessarily has a diameter greater than the pellets, it is possible that these pellets can move independently relative to each other. By modeling a large number of different random arrangements of pellets using the Monte Carlo code MCNP6, we were able to construct a probability distribution of the possible dose rates. Using a maximum pellet displacement off of the centerline of 0.25 mm (which assumes the source housing diameter is 0.5 mm greater than the pellet diameter), the FWHM of this distribution is 2.3%. Perhaps more interestingly, the mean dose rate of this distribution is 8% higher than the dose rate obtained when all of the pellets are perfectly aligned, indicating that while randomized arrangements do not vary by much in dose rate, allowing for some offset (and subsequently decreasing the source self-attenuation) can cause an appreciable increase in dose rate.

We then looked at using 2 mm diameter source pellets to match the Gamma Knife hole size, which reduced the number of pellets needed from 20 to 5 (changing the source height from 20 to 5 mm). This change led to a 32.5% increase in dose rate at isocenter for the 18 mm collimator. As we do not have an accurate model of the PerflexionTM system at the time of writing, we were not able to similarly evaluate the newest Gamma Knife generation. However, based on these results, we believe it is worthwhile to investigate the feasibility of modifying the Gamma Knife sources by reducing their dimensions along the beam line in order to reduce the effects of self-attenuation.

Gregory SZALKOWSKI, Tanxia QU (New York, USA), C-K Chris WANG
09:00 - 18:00 #17723 - Patient specific dose verification using a phantom duplicating the patient anatomy created with 3D-printing technology.
Patient specific dose verification using a phantom duplicating the patient anatomy created with 3D-printing technology.

Objective: The aim of this work is to establish and implement a patient specific end to end quality assurance methodology for dose verification in advanced radiotherapy applications using 3D-printing technology.

Methods: Eleven patient VMAT plans including either stereotactic or re-irradiation cases of primary or recurrent brain or head and neck tumors, created in Monaco TPS, were verified. A 3D-printer was used to construct a hollow phantom that duplicates the patient anatomical geometry, including bone structures, using the patients' planning-CT DICOM images. Special inserts were also constructed to position either a semiflex PTW (volume:0.125 cc) or a CC01 IBA (volume:0.01 cc) ionization chamber PTV and OARs. The hollow phantom was subsequently filled with water to simulate normal brain. The phantom was irradiated using the specific patient’s irradiation protocol including the IGRT step using CBCT with Elekta HexaPOD 6D robotic couch.  Phantom CBCT- images were co-registered with the patient-CT images in the TPS to accurately define ionization chamber positions. TPS calculations in the patient anatomy were calculated and compared with corresponding measurements.

Results: An excellent agreement (difference <4%, average=2.7%±1.2%) between measurements and TPS calculations were observed in the low dose gradient/high dose region within PTV. In the OARs region, the degree of agreement between measurements and calculations depend significantly on the definition accuracy of the position of the ionization chamber volume in patient anatomy as well as on the dose gradient in the region of measurement with differences being increased in the high dose gradient regions. In any case, differences < 10% (average=5.4%±2.4%) were observed with the measured dose being always lower than the accepted dose limit for the specific OAR.

Conclusion: The implemented methodology based on 3D-printing technology was found capable to verify the dose in clinically significant regions within the patient without the need of plan recalculation in the phantom anatomy.

 

Nikolaos GIAKOUMAKIS, Pantelis KARAISKOS (Athens, GREECE), Chryssa PARASKEVOPOULOU , Efi KOUTSOUVELI, Georgios KRITSELIS, Georgios KOLLIAS
09:00 - 18:00 #17846 - Polyetheretherketone (PEEK) implant can reduce postoperative artefacts and improve accuracy rate of delineation : a test in both pig and human.
Polyetheretherketone (PEEK) implant can reduce postoperative artefacts and improve accuracy rate of delineation : a test in both pig and human.

Background

Spinal stereotactic body radiotherapy (SBRT) delivers high doses of radiation and it is highly conformally focusing the radiation dose on the metastatic bone while sparing spinal cord. Postoperative SBRT dose planning relies on CT and MRI imaging. Polyetheretherketone (PEEK) is a new material of radiolucent character.

Aim is to compare the artefacts in CT and MRI scans caused by PEEK and Titanium rods implanted in pigs and humans.

Methods

In the pig spine specimen three groups of implants were sequentially inserted: a) Two Titanium rods, b) one Titanium rod and one PEEK rod, c) two PEEK rods. CT and MRI scans were acquired of all groups. A region of interest (ROI) was defined in order to measure the imaging noise caused by the rods. CT Houndsfield units (HU) were measured in ROIs and the image-noise were compared by calculating  artefact density standard deviation (SD).

The accuracy of spinal cord identification on MRI scans was compared on two patients who underwent spinal stabilisation.

Results

In the CT scans of pig specimen, the image-noise (artefact density standard deviation) was 63.5 HU for the titanium rods and 6.2 HU for the PEEK rods. There was a significant difference in image-noise between the two groups (P<0.01). The artefacts in the CT scans caused by the implanted rods were considerably lower for PEEK than for Titanium. For the two patients with respectively implanted PEEK and Titanium rods, it was only possible to identify the spinal cord for the patient with PEEK implants.

 Conclusions

PEEK rods created significantly less artefacts than Titanium rods in both CT and MRI scans, thus enabling more accurate spinal cord definition before SBRT. By using this new material, patients could benefit from a more precise and secure SBRT treatment  with less risk of radiation induced side-effects.

Miao WANG (Aarhus, DENMARK), Yasmin LASSEN-RAMSHAD, Esben Schjødt WORM, Simon Toftgaard SKOV, Haisheng LI, Anja HARBØLL, Kristian HØY, Ming SUN, Akmal SAFWAT, Ebbe Stender HANSEN, Kestutis VALANCIUS, Simon BUSS, Lise Nørgaard BENTZEN, Thomas BENDER, Morten HØYER, Cody BÜNGER
09:00 - 18:00 #17826 - Spontaneous intraocular air arising after placement of stereotactic frame.
Spontaneous intraocular air arising after placement of stereotactic frame.

Introduction: Although used since the last century, its application still can bring unexpected findings. It can be challenging after a craniotomy, requiring frame rotation and/or pins adjustment to avoid the bone flap. 

Objective: To report the spontaneous appearance of intraocular air immediately after stereotactic frame placement. 

Methods: A 61-year-old woman diagnosed with a left frontal tumor underwent microsurgery, confirming a fibrous meningioma. After complete resection, the tumor relapsed 4 years later. She elected to be treated with radiosurgery. A Leksell model G frame (Elekta, Sweden) was applied with fixation in a more basal manner than usual to avoid the bone flap of the previous left frontal craniotomy. She had eyelid edema immediately after injection of local anesthetic on the right eye. Immediate CT scan after the frame fixation showed the presence of intraocular air on the left eye (same side of craniotomy). This finding was absent on the MRI taken for planning a day earlier. Rigorous assessment did not show a bone fracture or pin slid into the orbit that would justify this finding. Ophthalmological infection was also ruled out. Radiosurgery underwent uneventfully, using a prescription of 15 Gy to the 50% isodose line. The patient reported a scotoma on the following day after radiosurgery. CT scan was repeated 8 days after GK showing complete resolution of intraocular air. Nevertheless, the patient continued to report a blind spot, later confirmed with a visual field exam. The patient was evaluated by a neuro-ophthalmologist who diagnosed a significant retinal pathology on the left eye. Intraocular air occurred ipsilaterally to the tumor and the craniotomy.

Conclusion: This is an unlikely concomitant occurrence of intraocular air accompanied by scotoma following stereotactic frame placement. Neuro-ophthalmologic investigation confirmed the co-existence of underdiagnosed retinopathy.

Juliete MELO DINIZ (SAO PAULO, BRAZIL), Antônio DE SALLES, Rafael COSTA LIMA MAIA, Aline Lariessy CAMPOS PAIVA, Bruno Henrique DALLO GALLO, Crystian WILIAN CHAGAS SARAIVA, Alessandra GORGULHO
09:00 - 18:00 #17717 - Stereotactic frame-based registrations methods for the Leksell Gamma Knife®.
Stereotactic frame-based registrations methods for the Leksell Gamma Knife®.

Introduction: The Leksell G-frame is designed to localize and immobilize the patient during imaging and treatment with e.g. the Leksell Gamma Knife®. The localization system uses the indicator box with N-shaped fiducials, to create a stereotactic space for tomographic studies used for registration in the Leksell GammaPlan®(LGP). Two new registration algorithms are proposed and evaluated on several tomographic image studies. The purpose is to investigate the registration differences between the LGP registration algorithm and the proposed registration algorithms in images where varying amount of distortion is present.

Materials and methods: 25 CT and MRI studies were stereotactically defined in a Leksell Gamma Plan 11.1 research version from which fiducial information could be exported for evaluation. LGP registers the corners of the stereotactic N derived from least-square fit of fiducials whereas the two proposed algorithms use the fiducial coordinates to minimize the distance of the fiducial to the theoretical fiducial N, either with respect to the mean or quadratic fiducial registration distance, which handles distortions differently. Differences in fiducial registrations and coordinates in stereotactic space were evaluated.

Results: The proposed registration methods proved stable and resulted in smaller mean fiducial distances compared to LGP; Mean Value method MR: 0.479±0.082mm, CT: 0.176±0.047mm; Quadratic method MR 0.484±0.081mm, CT: 0.179±0.050mm compared to LGP MR 0.559±0.088mm, CT 0.353±0.145mm. The quadratic formulation suppresses noise efficiently while the mean formulation reduces the effects of systematic fiducial deviations. The mean and max difference in stereotactical coordinates between registrations based on LGP vs the proposed formulations were 0.4mm and 0.9mm, respectively.

Conclusion: The small shift may be insignificant for most of the image sets analyzed. Larger deviations with LGP registrations (2D error) gave transformations resulting in larger deviation in the stereotactic volume. Further investigations are needed to evaluate stereotactic definitions.

Jonas JOHANSSON (Stockholm, SWEDEN)
09:00 - 18:00 #17865 - Tears: A Bizarre Cause of Collision in Gamma Knife Radiosurgery.
Tears: A Bizarre Cause of Collision in Gamma Knife Radiosurgery.

Background: With the availability of Perfexion and the Icon model of Gamma knife radiosurgery, no part of the brain is an exception for the treatment. 

Objective: For all practical purposes, the most common cause of the collision is not the patient’s head but the post or screw. Collision warnings distribute mostly at the anterior and the posterior ends of the head and less in the cranio-caudal direction. There is no other plausible source of collision in the radiosurgery. 

Case presentation: We have faced a difficult situation while administering gamma knife treatment to a 7-year-old boy with residual resistant acromegaly. The frame was placed equidistant keeping the nose in the center thereby centralizing the sellar region. All collision checks were confirmed, and no collision was reported, as the lesion was central and easily achieved with the treatment plan. Shortly after starting the treatment, the child got restless and started crying. After a while, the machine stopped the treatment indicating a collision error, but we could not find any source of contact.

Conclusion: The cone inside the treatment area is a collision sensor suspended on sensitive springs. The sensors’ function is to suspend treatment if the cone is displaced such that it creates an electrical connection with the collimator system. This shorting to the ground the trigger to prevent a mechanical collision between the fixated patient and the collimator. The sources are withdrawn to the park position and treatment stops. It seems that the patient’s tears, in this case, were sufficient to trigger the collision sensor. One can wonder if the system has become overly sensitive, in which case it would be recommended to inspect and perhaps change the springs. This case highlights the extreme sensitivity of the gamma gantry to avoid any unnecessary radiation or wrong delivery of the treatment. The treatment of pediatric patients under general anesthesia is another solution for this possible complication.

Manjul TRIPATHI (Chandigarh, INDIA)
09:00 - 18:00 #17654 - The reason for complying with the treatment time limit in plan competition for GKRS.
The reason for complying with the treatment time limit in plan competition for GKRS.

With the purpose of improving the quality of radiosurgery, there were for the first time two treatment plan competitions of brain stereotactic radiosurgery in 2018. They both have 5 target, prescription dose of 20Gy, and treatment time limitation in common. At the last minute 1st plan competition ignored the treatment time limitation on request from the users but 2nd plan competition kept it until the end. We analyzed the result of two competitions and figured out that the decision of keeping the treatment time limit or not was a key to ranking in GKS. ProKnow, 1st competition’s organizer, announced the result on website. It selected the top 50 among all participants with the individual information, acquisition score and the summary of the treatment plan. I analyzed the 7 people’s treatment plan registered in top 50 from the website and added one more plan that was one of my 2 treatment plans presented to the competition but not ranked in it. The result of RadiationKnowledge, 2nd competition’s organizer, took a little more time to be announced on the website and had only one gamma knife treatment plan in top 20 giving only individual information and acquisition score. I could review the plan information because the plan was mine. The first competition did not give the information of the treatment time but give the number of shots instead. We could anticipate the treatment time from the 3 plans that the owner of the plan had sent to me. Among 8 plans only one plan with 18 shots and 103 minutes kept the treatment time limitation. Seeing that the treatment plan with 26 shots had the treatment time of 146 minutes, the others must have exceeded the time limit of 120 minutes. The second competition must have kept the time limit of 90 minutes. The plan only recorded in the top 20 had the treatment time of 89 minutes with 19 shots. Even though the plans taking longer treatment time were certainly GKS planning for clinical treatment, the time limit should have kept to fairly compete in the game and make a right order in ranking. It seemed that the plan competition was to evaluate the ability to meet the condition not to find the highest score. If the first competition’s organizer had commented about this, the participants would have noted that they should comply with the time limit from next plan competition, such as RadiationKnowledge's plan competition.

Weon-Seop SEO (SEOUL, KOREA), Chang-Kyu PARK, Seok-Keun CHOI, Bong-Jin PARK
09:00 - 18:00 #17745 - The use of correction factor free detectors to validate ultra-small field dose distributions.
The use of correction factor free detectors to validate ultra-small field dose distributions.

Purpose: Ultra-small field dosimetry (<1cm) is challenging due to perturbation effects and 
volume averaging. Recently, small field correction factors have been introduced to compensate 
for the the varying responses of different detectors in radiosurgical fields. We demonstrate that 
data acquired and validated with detectors not requiring correction factors, such as the W1 
(Standard Imaging, Madison, WI) and Gafchromic film (Ashland, Bridgewater, NJ), yields 
excellent agreement between plans created in the Multiple Met (MME) Element (Brainlab, 
Munich, Germany) and phantom measurements. 
 
Methods: Output factors were acquired on a Truebeam STX (Varian Medical Systems, Palo 
Alto, CA) with a flattening filter free 6 MV beam using an Exradin W1 scintillator. Treatment 
plans for 41 targets were validated in MME: 5 with the W1 and 36 with Gafchromic EBT3 or XD 
film. Target sizes ranged from 0.06 cc to 0.6 cc and 0.03 cc to 1.7 cc for the W1 and film 
validations, respectively. Treatment plans were planned and delivered on MaxHD (IMT, Troy, 
NY) and Baby Blue (Standard Imaging, Madison, WI) phantoms. Phantom alignment was 
performed before and during delivery using Brainlab’s ExacTrac with thresholds of 0.5mm and 
0.5°. 
 
Results: All plans validated with film and the W1 had good agreement with calculations. 
Gamma scores >96% (2%/1mm, 10% dose threshold) were achieved for all film validations for 
targets ranging from 0.03cc to 1.7cc. W1 point dose measurements were <1.5% of calculation 
for all but the 0.06cc target, at which the target size is comparable to the W1 dimensions.  
 
Conclusions: Using a detector with a unity correction factor (or applying proper correction 
factors to an appropriate detector, such as those available in IAEA’s TRS 483) to collect and 
validate data is essential for an accurate machine build.
Lauren WEINSTEIN (South San Francisco, USA), Matthew SKINNER
09:00 - 18:00 #17809 - Use of a Trial Setup to Assess Patient Acceptability for Mask-Based Gamma Knife Treatment.
Use of a Trial Setup to Assess Patient Acceptability for Mask-Based Gamma Knife Treatment.

Purpose: Mask-based stereotactic radiosurgery (SRS) on the Gamma Knife (GK) is facilitated by intra-fraction motion management (IFMM) and cone beam computed tomography (CBCT). The purpose of this study is to evaluate the use of a trial setup during mask simulation to determine patient eligibility and acceptability for mask-based GK-SRS.

Methods: Patients triaged to masked-based GK-SRS undergo a simulation appointment to manufacture a patient-specific mask and headrest, and acquire a reference CBCT for treatment planning. During simulation, while the mask sets on the patient, a trial setup using the IFMM device was performed by tracking a reflective marker on the patient’s nose through the stereoscopic camera. Passive tracking of the marker was performed for 10-20 minutes to assess both the magnitude of patient motion, and patient tolerability to the treatment setup position as large motions tracked via the IFMM system triggers treatment interruption during GK-SRS delivery.

 Results: Mask simulations on the GK were performed on 92 patients. Twelve patients were subsequently aborted for SRS due to various reasons following trial setup: extreme claustrophobia (2), large range of motion on IFMM due to poor performance status (2), triaged to linear accelerator treatments due to number of lesions or lesion size (6), triaged to surgical intervention (1), and patient declined GK-SRS (1). Due to collision risks identified in the pre-planning process, 8 patients were re-simulated with a new mask or foam headrest prior to GK-SRS. The IFMM threshold for GK-SRS was increased from 1.5 mm to 2.0 mm for 5 patients based on motion observed at trial setup.

Conclusions: A trial setup with the mask and IFMM system during the simulation appointment is useful in identifying patient eligibility for mask-based SRS. Identifying patient specific factors, such as claustrophobia and poor performance status, assists with patient comfort measures or triage to other more suitable treatment options.

Winnie LI, Messeret TAMEROU, David SHULTZ, Normand LAPERRIERE, Barbara-Ann MILLAR, David JAFFRAY (Toronto, CANADA), Caroline CHUNG, Catherine COOLENS
09:00 - 18:00 #17742 - Using a high frequency sampling electrometer to measure directly six time related parameters in one acquisition.
Using a high frequency sampling electrometer to measure directly six time related parameters in one acquisition.

This study is to report a novel method to measure six time related parameters: 1) timer accuracy; 2)  timer error; 3) timer linearity; 4) time between two shots; 5) time for sector passing the 4mm cone when traveling to 16 mm cone; 6) transient time that corresponding to shutter dose. This method uses a high frequency sampling electrometer to measure time directly vs the previous method that measure dose and calculate time. Current of every 0.05 sec is collected using a SunNuclear PCElectrometer in the standard GK icon QA setup over one composite acquisition of four shots of 1, 3, 10, and 20 min, respectively. The source sectors start from the sector off position, pass 4mm cone, moves to a 16 mm cone position for nominal exposure time of 1 min, then pass the 4mm cone again, and move back to the sector off position for a short period of time (time between two shots), then repeat the cycle for 3, 10, and 20 min settings, respectively. A MATLAB program was written to graph and calculate 1) timer accuracy of 59.8, 179.7, 599.5 and 1199.1 sec for nominal setting of 60, 180, 600 and 1200 sec, respectively; 2) timer error of 0.40 sec; 3) Timer linearity of R square of 1.0; 4) time between two shots of 4.9 sec; 5) time for sector passing 4mm cone of 0.4 sec; 6) transient time of 0.24 sec for the sectors to reach their full exposure positions.  This transient time is what Gamma Plan uses to account for the shutter dose.  In conclusion we have developed a semi-automatic method to measure time related parameters objectively, accurately, and efficiently by using a programmable high frequency sampling electrometer.

Tanxia QU (New York, USA), Kenneth BERNSTEIN, Douglas KONDZIOLKA
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P11
09:00 - 18:00

EPOSTER - 11 Pituitary
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17590 - Radiosurgery insulin like growth factor 1 immediate response in growth hormone residual adenoma.
Radiosurgery insulin like growth factor 1 immediate response in growth hormone residual adenoma.

Introduction. Patients with pituitary growth hormone secretor benign adenoma has demonstrate a consistent functional response to radiosurgery. This clinical observation present the immediate insulin like growth factor 1 response to ionizing radiation exposure single dose in residual adenoma.

Method. A 49yo male with acromegalic and right hemparesis 4/5 with previous partial resection of pituitary adenoma one year before and vascular intervention for left carotid lesion was programed for radiosurgery. His image studies showed 2.1 cc residual tumor on left cavernous sinus. Five days previous to gamma radiosurgery growth hormone level was 5.04 ng/ml, on treatment day insulin like growth factor 1 was measured previously and inmediatelly after radiation exposure, one and four hours later. 

Results. Insulin like growth factor 1 in ng/ml was as follows: previous 754, immediately after 915, one hour later 954 and four hour later 901. No growth hormone level and fluctuation was considered.

Conclussion. Insulinic growth factor 1 is used in response to treatment follow up in growth hormone pituitary secretory adenomas, his consistency has been tested before. Insulin like growth factor 1 measurement has been reported after surgical procedures previously as a treatment response prognostic factor. In radiosurgery the initial response level rise and his slow return suggest an immediate response at celular level releasing insuline like growth factor 1 and stroma acute microvascular response increasing metabolic evironmental flow and feedback loop of growth hormon secretion, however there is not ready available information related to microscopic morphology, ultrastructural and functional changes in the tumor cells and peritumoral stroma as a result to single dose radiosurgery. In this investigation field is needed basic research updated information wich is not yet available after ionizing radiation exposure in single dose. This justifies enphasize the effort in basic research in supraselar growth hormone secretory adenomas.

Vinicio TOLEDO (GUADALAJARA MEXICO, MEXICO), Marco BARAJAS, Carlos PATARROYO, Fernando ZAZUETA
09:00 - 18:00 #17805 - Stereotactic radiosurgery in the combined treatment for functional and nonfunctional pituitary adenomas.
Stereotactic radiosurgery in the combined treatment for functional and nonfunctional pituitary adenomas.

Stereotactic radiosurgery can be used for patients with residual or recurrent pituitary adenoma (PA) that are refractory to surgical and medical therapies.

Materials and methods. 35 patients (19 men and 16 women) with pituitary macroadenoma were treated from 2011 till 2017. 23 patients had single-fraction stereotactic radiosurgery (SRS) on Linear accelerator «Trilogy + BrainLab» and 12 patients had fractinated stereotactic radiosurgery(fSRS) on CyberKnife (CK). The diameter of PA ranged from 1,1 cm to 3,4 cm. 32 patients had previous neurosurgical operations. Hormonally inactive pituitary adenomas were observed in 5 cases. 17 patients had acromegaly (the level of GH was from 24 mmol / l to 216 mmol / l), in 10 cases was prolactinoma (LH level was from 88 ng / ml to 336 ng / ml), in 3 cases was Cushing disease with increased level of ACTH (the level of ACTH ranged from 100 pg / ml to 1250 pg / ml). The marginal doses for the tumors were for LINAC SRS 13 Gy to 17 Gy (median, 14.1 Gy), for CK SRS 18-25 Gy in 3-5 fractions.

Results: The median follow-up of patients was 14 months (range 8-36 months). There were not radiation-induced acute or late toxicities in any case, except for one case of apoplexy in the pituitary gland 4 months after SRS. The tumor had decreased in size in 19 patients and remained stable in 16 patients. 24 patients had a decrease in the level of hormones after radiosurgery.

Conclusion: Single-fraction SRS may represent a convenient approach to patients with small and medium-sized PA away at least 2 mm from the optic chiasm, whereas FSRT is preferred over SRS for lesions >2.5-3 cm in size and/or involving the anterior optic pathway.

Vladyslav BURYK (Sigulda, LATVIA), Maris MEZECKIS, Olga CHUVASHOVA, Igors AKSIKS, Dace SAUKUMA, Jelena NIKOLAJEVA, Maris SKROMANIS
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P12
09:00 - 18:00

EPOSTER - 12 Prostate (GU)
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17648 - Early experience and results from the implementation of stereotactic body radiotherapy in localized prostate cancer.
Early experience and results from the implementation of stereotactic body radiotherapy in localized prostate cancer.

Purpose

The purpose of this study is to present the results, in terms of efficacy and safety, of the implementation of Stereotactic Body Radiotherapy (SBRT) as a definitive treatment of patients with localized prostate cancer in Hygeia Hospital, Athens, Greece.

Materials and Methods

Five patients with low-risk prostate cancer, Stage T1-2 with combined Gleason scores of 6 and median PSA below 8ng/ml, without androgen deprivation (ADT), were enrolled for SBRT treatment following a scheme of 35Gy delivered in 5 fractions in a period of two weeks. Assuming an alpha/beta value of 1.5, the biologically equivalent dose is 78Gy. The clinical target volume (CTV) included the prostate and depending on risk stratification, the base of seminal vesicles. Additional margins of 3-5mm were used to form the Planning Target Volume (PTV). Patient plans were calculated on Elekta Monaco TPS and treated on an Elekta VersaHD Linac using a 10 MV Flattening Filter Free (FFF) beam. Patients were given dietary and bladder filling instructions and a rectal enema prior to every fraction. Patient positioning was verified with CBCT image-guidance prior and post treatment. To evaluate the average variation of rectum position, image registration was performed between original CT and each CBCT. Rectum and bladder toxicity was evaluated.

Results

No significant rectal (grade1) or urinary (grade1) toxicity was observed for any of the patients during follow up. The toxicity profile was compared to past conventionally fractionated dose-escalation and hypofractionated studies. This is due to the combination of a strict and well-defined protocol which included careful bladder and rectal preparation, narrow margin expansion together with a strict pre-and post- treatment imaging protocol.

Conclusion

SBRT as a definitive therapy in localized prostate cancer has been successfully applied. All patients demonstrated normal PSA levels and low toxicity while maintaining high quality of life.

Georgios KRITSELIS (ATHENS, GREECE), Chryssa PARASKEVOPOULOU, Nikolaos GIAKOUMAKIS , Efi KOUTSOUVELI , Pantelis KARAISKOS, Georgios KOLLIAS
09:00 - 18:00 #17843 - First UK experience of Hydrogels to Enhance Rectal Sparing during Prostate SBRT.
First UK experience of Hydrogels to Enhance Rectal Sparing during Prostate SBRT.

First UK experience of Hydrogels to Enhance Rectal Sparing during Prostate SBRT

Background

The use of hydrogrel spacers to help spare the rectum is growing in popularity in the field of radiation therapy including brachytherapy. In 2015 The London Clinic became the first UK hospital to use hydrogel SpaceoarsTM by AugemixTM. Since then several patients have had them inserted prior to radiotherapy or SABR treatment.

Method

The first three patients were selected who have had SBRT treatment for detailed analysis and follow up. Fiducials and Spaceoar were inserted in one session in day case procedure. The BKTM Ultrasound stepper unit was used transrectally to guide their insertion, which was performed via the transperineal route, whilst the patient was in the lithotomy position. A CT planning scan and MR T1 and T2 sequences were then performed 7 days later for each patient. The resulting scans were imported, fused and planned using MultiplanTM for treatment using PACE protocol(36.25Gy in 5 fractions) on the CyberknifeTM SBRT platform. Dose Volume Histogram (DVH) calculated and volumes are noted at the 37, 36.25, 35, 30, 25 and 20 Gy levels. Three past SBRT prostate patient treatment plans with Spacoar present were compared to the average data set obtained for Spacoar free plans.

Results

Resulting data from the DVHs were compared with the volume in terms of percentage and cubic centimetres. Differences observed were 37Gy spaceoar(n=3) 0.07% 0.07cc without(n=4) 1.53% 1.03cc, 35Gy 0.37% 0.27cc without 3.6% 2.881cc, 30Gy spaceoar 1.93% 1.14cc without 9.55% 6.42cc and 20Gy spaceoar 13.07% 8.29cc without 27.10% 18.48cc.

Conclusions

There was a reduction of dose to rectum as predicted2,3, particularly at the higher dose levels which are thought to be the areas where significant side effects occur. Typically a 1cm gap was generated between the prostate and the rectum. No significant toxicity has been reported over 4 years, in line with predicted results albeit for a small group of patients.

Nigel Ashley RICHMOND (London, UK), Simon STEVENS, Katrina FINNEGAN, Mark BRAY-PARRY, Jan KONIECZEK, Isabel HO, Joshua GESNER, Steven CRITCHLEY
09:00 - 18:00 #17893 - Quality of life after robotic radiosurgery of primary prostate cancer: sexual domain.
Quality of life after robotic radiosurgery of primary prostate cancer: sexual domain.

Introduction: Sexual domain is important aspect in Quality of Life (QoL) for sexualy active prostate cancer (pCa) patients (pts). Prescribed doses, regimens, treatment techniques and other aspects vary among clinics. Analysis of QoL data in every particular clinic helps in decision making for patients between different treatment methods.

Materials and methods: From June y.2016 to January 2019 26 sexually active patients who had received FSRS to primary prostate cancer filled EPIC Questionaire Sexual domain before treatment and during follow-up starting from 3 months post treatment. Prescribed dose was 35-36.25Gy with homogenous dose distribution (normalised 70-80% isodose line) to prostate (low-risk) or prostate + 1-2cm seminal vesicles (intermediate and high risk pCa) added 5-3mm for PTV. Intermediate and high risk pCa patients were treated focally increasing dose above 40Gy to dominant lesion on MRI/PSMA PET-CT. Follow-up was 3 - 12 months (median 6.5 months). Patients receiving androgen deprivation therapy were excluded. Relation of deterioration in EPIC score with clinical stage and correlation of target volume was analyzed with SPSS Statistics software (Kruskal-Wallis H, Spearman's rank correlation,) . Baseline EPIC score was 158-600 (median 462.5).

Results: Overall EPIC score in Sexual domain was reduced on 4.16-44.50% (median 12.5%) in following months after treatment. For 3 (11.54%) patients EPIC score returned to baseline afterwards, for 14 pts (53.85%) remained deteriorated (median difference -16.6%) and for 9 pts (34.62%) score raised above baseline on 5-35% (median +15.82%). There was no correlation found in EPIC score changes and clinical stage or size of the target volume.

Conclusions: Prostate radiosurgery has different impact on sexual QoL in particular follow-up period. For some patients it showed positive effect what might be linked to psychological aspect of completed treatment and reduced PSA. There were not found risk factors what might be linked with reduced sexual QoL. Further data analysis for correlation of EPIC score changes with radiation dose to anatomical structures, such as neuro-vascular bundle, penile bulb and external urethral sphincter, has to be done in larger population and in longer follow-up to clarify risk factors for reduced sexual QoL.

Maris MEZECKIS (Sigulda, LATVIA), Kirils IVANOVS, Egils VJATERS, Sandra CIPKINA, Vladislav BURYK
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P14
09:00 - 18:00

EPOSTER - 14 Spine
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17535 - Dosimetric impact of nerve roots sparing in spinal metastases stereotactic body radiotherapy treatment with Cyberknife.
Dosimetric impact of nerve roots sparing in spinal metastases stereotactic body radiotherapy treatment with Cyberknife.

Purpose

The aim of this analysis was to assess whether preservation of nerve roots (NR) doesn’t deteriorate treatment plan of spinal metastasis treated in SBRT. Radiation-induced neuralgia may occurs in 15% of cases, which is painful and a cause of the decrease in patients' quality of life.

Patients and Methods

Data concerning 11 patients treated for spinal metastases at levels between T12 and L5, in one or 3 fractions, were retrospectively studied. The prescribed dose were between 18 and 27Gy. All patients had pre-treatment imaging with CT and MRI scanner in high resolution (CT used for dose calculation, the T1 gado sequence for tumor delineation and the T2 sequence for NR, SC and CE delineation). For each patient two treatment plans were calculated, the first one without dose constraint to NR, and the second one with. All plans were analyzed according to: the tumor coverage, the quality index and the dose constraint to SC and CE. For SC, CE and NR, the nearest maximal dose was recorded. For NR, the mean dose was computed too. Parameters of the two groups were compared by a Student’s t-test and are given with 95% confidence intervals.

Results

For each patient, both plans respect tumor coverage and dose constraint to OAR. The quality index results are similar for both plans in each patient, no significant difference was found. For SC, the mean nearest maximal doses were 12.2Gy and 11.4Gy (P=0.41), respectively for plan without optimization on NR and with, in 3 fractions. For CE, the mean nearest maximal doses were 15.3Gy and 15.7Gy (P=0.49) for single fraction and 23.6Gy and 22.7Gy (P=0.45) for 3 fractions. For NR, the mean nearest maximal doses were 17.8Gy and 14.8Gy (P=0.005) for single fraction and 24.5Gy and 23.3Gy (P=0.21) for 3 fractions. The mean doses to NR were, for single fraction treatment, 14.56Gy and 12.09Gy (P=0.04) and 19.52Gy and 18.44Gy (P=0.37) for 3 fractions treatment.

Conclusion

The decreasing of NR dose constraint allowed to achieve clinically acceptable treatment plans and all quality index obtained were similar. The optimizing of NR dose constraints does not deteriorate the nearest maximal dose to SC and CE. For single fraction, the addition of dose constraint to NR significantly reduces their nearest maximal dose by about 13%. For plans delivered in 3 fractions, this study doesn’t have enough patients to achieve significant results.

Florence BARTIER (AMIENS), Alexandre COUTTE, Michel LEFRANC
09:00 - 18:00 #17709 - Early experience with spine radiosurgery planning and patient specific QA with a dedicated spine SRS treatment planning system.
Early experience with spine radiosurgery planning and patient specific QA with a dedicated spine SRS treatment planning system.

                The initial experiences with the BrainLab Elements Spine Stereotactic Radiosurgery treatment planning system (TPS) are described. Spine Elements includes multi-modality image fusion, spine curvature correction, automatic target and critical structure segmentation, and a VMAT-based treatment planning system capable of Monte Carlo dose calculation. The software was accepted and commissioned in 2018 and five patients have since been treated using a Novalis Tx linear accelerator with the BrainLab ExacTrac system for localization. Of the five patients, three were single fraction SRS (12-16 Gy) and two were fractionated in 3 and 5 fractions. The patient-specific QA results when recomputing the patient plan on an Octavius 4D phantom geometry were analyzed using gamma analysis. Confidence in the initial commissioning was ensured via MPPG 5.a and an IROC Spine phantom accreditation using the Monte Carlo algorithm. Gamma analysis was performed using passing criteria of 3% and 1 mm. Global gamma was used relative to the maximum dose value in the calculated volume. All gamma analysis results comparing an Octavius 1000SRS array measurement with calculation were above 98% using 2%/2mm local gamma. For patient plans, average gamma passing rate was 99.2% with a standard deviation of 1.0%. Median dose deviation across all patients is 1.1% with a standard deviation of 0.3%. Accurate dosimetric results were obtained through IROC accreditation, MPPG 5A, and patient QA plans for the first five patients thereby validating the dose calculation of a novel spine SRS TPS utilizing Monte Carlo.

Daniel SAENZ, Richard CROWNOVER, Niko PAPANIKOLAOU (San antonio, USA)
09:00 - 18:00 #17565 - Evaluation of spine dose during SBRT treatment of spine metastases.
Evaluation of spine dose during SBRT treatment of spine metastases.

Objectives: To evaluate the actual dose received by the spinal cord during SBRT treatment of spine metastases due to the variation in patient position.

Methods: 5 patients with 7 different spine metastases were planned and treated using SBRT technique, the dose delivered using RapidArc modality on Varian linear accelerator 2100CD with Exact couch. All patients were immobilized using SBRT rails and customized vacuum bag, arms were above the head on Posirest arm support, knee and feet support were used. The dose was initially selected to be 24Gy in 3 fractions. Dose constrains for the spinal cord were taken from the AAPM report TG101. To verify the patient setup, 2 orthogonal KV images were used, once position is corrected then CBCT image will be acquired.

Target volume and spinal cord contours were copied from the CT and pasted on the CBCT, they were adjusted to match the bony landmark. Plans were created using the same treatment field with the isocenter positioned as on the actual treatment.

To be able to use the CBCT for dose calculation, CBCT calibration curve was created in the Eclipse TPS. Constancy of the HU is checked as part of the monthly quality control of the linear accelerator.

Results: Doses at the following spine volumes were compared: 1.2cc, 0.35cc, maximum dose and 10% of the partial spine volume. Mean of dose differences in percent were found to be lower in CBCT image for the specified volumes respectively (1.6 ± 2.1, 1.8 ± 2.9, 1.5 ± 4.0 and 0.4 ± 3.0)

Conclusion: SBRT for spine is a safe procedure even though there is small variation in patient setup, it still shows that the dose constrains to the spine are well maintained. Next step is to consider the RTOG631 dose prescription of 16-18Gy in a single fraction.

Marouf ADILI (Riyadh, SAUDI ARABIA), Abdulaziz ALHAMAD, Bilal MUHAMMAD
09:00 - 18:00 #17620 - Evaluation of spine structure stability at different locations during SBRT.
Evaluation of spine structure stability at different locations during SBRT.

Purpose: To evaluate spine movement and spine position stability during stereotactic body radiotherapy (SBRT).

Methods and Materials: This study included 123 patients treated with spine SBRT. We analyzed different locations within the spine using system log files generated during treatment, which contain information about differences in the pretreatment reference spine positions by CT versus positions during SBRT treatment. We evaluated mean spine motion and intra/interfraction motion. We defined and evaluated spine stability and spine significant shifts (SSHs) during treatment.

Results: We analyzed 462 fractions. For the cervical (C) spine, we observed the greatest shifts in the anterior-posterior (AP) direction (2.48 mm) and in pitch rotation (1.75 deg). The thoracic (Th) spine showed the biggest shift in the AP direction (3.68 mm) and in roll rotation (1.66 deg). For the lumbar-sacral (LS) spine, the biggest shift was found for left-right (LR) translation (3.81 mm) and roll rotation (3.67 deg). No C spine case exceeded 1 mm/1 deg for interfraction variability, but 7 of 54 Th spine cases exceeded 1 mm interfraction variability for translations (maximum value, 2.5 mm in the AP direction). The interfraction variability for translations exceeded 1 mm in 2 of 24 LS spine cases (maximum value, 1.7 mm in the LR direction). Only 13% of cases had no SSHs. The mean times to SSH were 6.5±3.9 min, 8.1±5.9 min, and 8.8±7.1 min for the C, Th, and LS spine, respectively, and the mean recorded SSH values were 1.6±0.66, 1.43±0.33, and 1.46±0.47 mm/deg, respectively.

Conclusion: Positional tracking during spine SBRT treatments revealed low mean translational and rotational shifts. Patient immobilization did not improve spine shifts compared with our results for the Th and LS spine without immobilization. For the most precise spine SBRT, we recommend checking the patient’s position during treatment.

Lukas KNYBEL (Ostrava, CZECH REPUBLIC), Jakub CVEK, Zuzana CERMAKOVA, Michaela POMAKI, Jaroslav HAVELKA, Kamila RESOVA
09:00 - 18:00 #17870 - Leksell frame fixation at maxilla for treating upper cervical spine lesions: nuances and our experience.
Leksell frame fixation at maxilla for treating upper cervical spine lesions: nuances and our experience.

Background: Traditional restriction of foramen magnum as the lower limit for target location for GKRS makes treatment of upper cervical spinal lesions formidable. Leksell frame fixation above supraorbital margins helps in achieving targets up to axis vertebra level. To target lesions in upper cervical spine with ensured immobility remains a challenging task. We describe our experience of treating lesions located in or extending into upper cervical spine while ensuring immobilisation and the precision of treatment. 

 

Material and Methods: We treated three cases of upper cervical spinal lesions (2 intradural extramedullary tumors and one skull base lesion). To minimize the movement at craniovertebral junction, Philadelphia collar was placed and frame was docked on it. The constant relative head neck position was maintained by keeping glabellar-floor and sternal-floor distance constant. Patient positioning system (PPS) and docking gamma angle were maintained at same values throughout the procedure. 

 

Results: All patients tolerated the procedure well. There was no complication at one-year follow up interval. One patient showed >50% tumour size reduction at one-year follow up. 

 

Conclusion: We tried to push the limits of stereotactic frame by fixing it on maxilla while maintaining immobilization by using strict protocol. Zygomatic process of maxilla might be considered a potential alternate site for frame fixation to target lesions upto C3 vertebra. The well-established dose algorithm for Cyberknife/LINAC system helps in validation of safe dose range for spinal lesions. This proof of concept model also facilitates treatment of lesions in patients with bony defects of previous surgeries (e.g. bifrontal decompressive craniectomy etc.).

 

Manjul TRIPATHI (Chandigarh, INDIA), Kanchan MUKHERJEE
09:00 - 18:00 #17869 - Linac-Based Radiosurgery in Spinal Tumors: Institutional Report.
Linac-Based Radiosurgery in Spinal Tumors: Institutional Report.

Purpose: to report local control and tolerance of stereotactic body radiotherapy (SBRT) in patients with spinal tumors.

 Materials and Methods: SBRT was delivered with LINAC (Linear Accelerator), volumetric modulated-arc therapy (VMAT) and image guided radiotherapy (IGRT). The primary end points were toxicity, clinical local control with radiographic study every 3 month and we use the common terminology of Criteria for Adverse Events v4.0 (CTCAE).

 Results: between September 2016 and November 2018, a total of 28 patients and 41 lesion were irradiated with a median dose of 25Gy(16-50Gy) in 3(1-5) fractions. With a follow up of 15.3 months and a mean age of 62 years old, we found 32(78%) metastatic lesions and 5(12%) primary lesions of spine, all without prior radiotherapy. The most frequent spinal areas were 25 thoracic, 12 lumbar, 2 cervical, 2 sacrum  respectively.  A single fraction was delivered in 11 cases (39%), while a 3-5fractions scheme was used in 17 (61%). The most common histological metastasis lesion was lung and prostate adenocarcinoma. Clinical local control at 10 months was 80% and no cases of Grade 3-4 toxicity were reported.

 Conclusion: SBRT is an effective treatment to achieve local control in spinal metastases. Our results appear comparable to previous reports analyzing spine SBRT.

Daniel DAVALOS, Lucas CAUSSA (Córdoba, ARGENTINA), José Máximo BARROS, Diego FERNANDEZ, Caroline DESCAMPS, Maria Fernanda DIAZ VAZQUEZ, Diego FRANCO, Enrique HERRERA, Emilio MEZZANO, German OLMEDO, Egle AON, Gustavo FERRARIS
09:00 - 18:00 #17752 - The Feasibility of Spinal Stereotactic Radiosurgery for Spinal Metastasis with Epidural Cord Compression.
The Feasibility of Spinal Stereotactic Radiosurgery for Spinal Metastasis with Epidural Cord Compression.

Purpose: To investigate the effectiveness and safety of spinal stereotactic radiosurgery (SRS) in treating spinal metastasis with epidural spinal cord compression (ESCC).

Materials and Methods: During 2013–2016, 149 regions of spinal metastasis in 105 patients treated with single-fraction (12–24 Gy) spinal SRS were reviewed. Cord compression of Bilsky grade 2 (with visible cerebrospinal fluid [CSF]) or 3 (no visible CSF) was defined as ESCC. Local progression (LP) and vertebral compression fracture (VCF) rates after SRS were evaluated using multivariate competing-risk regression analysis.

Results: The 1-year cumulative incidences of LP for Bilsky grades 0 (n = 80), 1 (n = 39), 2 (n = 21), and 3 (n = 9) were 3.0%, 8.4%, 0%, and 24.9%, respectively. ESCC did not significantly increase the LP rate (no LP for grade 2; subhazard ratio [SHR] for grade 3, 4.521; p = 0.246). The 1-year cumulative incidences of VCF for Bilsky grades 0, 1, 2, and 3 were 6.6%, 5.2%, 17.1%, and 12.1%, respectively. ESCC may increase VCF risk (SHR for grade 2, 5.368; p = 0.035; SHR for grade 3, 2.215; p = 0.460). The complete or partial pain response rates after SRS were 79%, 78%, 53%, and 63% for Bilsky grades 0, 1, 2, and 3, respectively (p = 0.008). No neurotoxicity of grade ≥3 was observed.

Conclusions: Spinal SRS for spinal metastasis with Bilsky grade 2 ESCC did not increase the LP rate, was not associated with severe neurotoxicity, and showed moderate VCF and pain response rates.

Yi-Jun KIM, Jin Ho KIM (Seoul, KOREA), Kyubo KIM, Hak Jae KIM, Eui Kyu CHIE, Kyung Hwan SHIN, Hong-Gyun WU, Il Han KIM
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P16
09:00 - 18:00

EPOSTER - 16 Other Benign
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #17760 - Analysis of 12 Cases of Solitary Fibrous Tumor/Central Hemangiopericytoma Treated with Gamma Knife.
Analysis of 12 Cases of Solitary Fibrous Tumor/Central Hemangiopericytoma Treated with Gamma Knife.

Objective: To summarize the effectiveness and efficacy of gamma knife in the treatment of solitary fibrous tumor/central hemangiopericytoma. Methods: The clinical data and follow-up results of 12 patients (2/10) with solitary fibrous tumor/central hemangiopericytoma treated with gamma knife from 2006 to 2016 were retrospectively reviewed to perform summary analysis. Results: All patients were followed up for 11 to 47 months, with an average of 29 months, including 10 cases with significantly decreased diameters of tumors at 3 to 4 months after the gamma knife treatment, 4 cases with recurrences and 2 cases with intracranial metastasis. No adverse reactions such as neurological injury or edema reaction were found in all patients after gamma knife treatment. Conclusion: Gamma knife is a safe and effective treatment for solitary fibrous tumor/central hemangiopericytoma, especially for residual or recurrent tumors after operations, with a satisfactory tumor control rate.

Yiguang LIN, Dong LIU (Tianjin, CHINA), Desheng XU
09:00 - 18:00 #17891 - Cisternae Oculomotor Schwannoma Treated With Gamma-Knife.
Cisternae Oculomotor Schwannoma Treated With Gamma-Knife.

Introduction:Cisternae Oculomotor Nerve Schwannomas (ONS) are rare and of difficult surgical approach. These lesions can present as ophthalmoplegic migraine.

Objective:To describe unilateral third nerve palsy without diplopia diagnosed due to an ONS. It was submitted to Gamma Knife Radiosurgery (GKR).

Methods:Detailed review of the literature using Pubmed identified few reports of presumed schwannomas affecting the third A 55-year-old woman presented with progressive abduction of the right eye during the period of 3 years, accompanied of eye irritation and light sensitivity. There was dilation of the right pupil without diplopia with preserved consensual reflex. Magnetic resonance imaging (MRI) revealed an 8.0 x 7.0 mm enhancing lesion occupying the right pre-pontine cistern, 3 mm away from the right optic tract. There was an important atrophy of the right third cranial nerve near the brainstem. Tumor volume was 309.2mm3. She was treated with GKR, the lesion received a total dose of 12Gy prescribed to the 50% isodoseline. Four isocenters of 4 mm collimator were used. Treatment time was 35 minutes. There were no complications and the patient was discharged on the same day. 

Conclusions:GKR is well described for schwannomas. This is a case of atypical location treated with excellent sparing of eloquent structures, specially the optic tract. 

Aline Lariessy CAMPOS PAIVA (Sao Paulo, BRAZIL), Alessandra GORGULHO, Rafael COSTA LIMA MAIA, Juliete MELO DINIZ, Tomás DE ANDRADE LOURENÇÃO FREDDI, Bruno Henrique DALLO GALLO, Antonio DE SALLES
09:00 - 18:00 #17867 - Current Status of Radiosurgery in India.
Current Status of Radiosurgery in India.

Though established as a treatment modality for various neurosurgical ailments, radiosurgery is yet to establish its firm feet in India. Gamma knife radiosurgery (GKRS) is considered a natural extension to microneurosurgery but there are competitive and supplemental interests. First gamma knife unit in India was established in 1996 at PD Hinduja Hospital, Mumbai shortly followed by AIIMS, New Delhi. At present there are 6 functional gamma knife centres in India. Out of these, 4 are at government teaching institutes while 2 at private centres. 4 centres are working on Perfexion, one with 4C and another with the B model of Gamma knife. There are 6 centres practising cyberknife radiosurgery and many more are yet to come. In comparison to Gamma knife, there are more centres coming up with Cyberknife because of logistic reasons. There is need of many more centres to take care of skewed facility patient ratio. The majority of the patient population is of benign intracranial pathologies and vascular malformations. This is in contrast to the western practice, where intracranial metastasis constitutes the majority of the patient population. One important reason for the same is nearly universal absence of medical insurance and prevailing nihilism in general population. With increasing awareness among neurosurgeons and publicity of non-invasive nature of radiosurgery with publications establishing its efficacy in long term, radiosurgery is now becoming a regular knife in neurosurgical armamentarium. 

Manjul TRIPATHI (Chandigarh, INDIA)
09:00 - 18:00 #17798 - Fractionated radiotherapy for benign brain tumors using mask system of Leksell Gamma Knife Icon.
Fractionated radiotherapy for benign brain tumors using mask system of Leksell Gamma Knife Icon.

Object: Leksell Gamma Knife Icon enables us to apply new methods of immobilization using mask fixation and the option of fractionated treatment. This provides exceptional accuracy and precision of radiosurgery, making it a possibility for many more disease types and many more patients to be treated.

Methods: We retrospectively analyzed 67 patients (69 times) with benign brain tumors who underwent fractionated radiotherapy using mask system of Gamma Knife Icon between September 25th, 2017 and December 31th, 2018 at Rakusai Shimizu Hospital. The most common disease was meningioma (38 patients), followed by vestibular schwannoma (12), craniopharyngioma (7), pituitary adenoma (6) and other schwannomas (4). The reasons of fractionated treatment were large tumor volume (24 patients), recurrence (10) and neurological critical location (45). For higher accuracy, we changed the upper limit of the HDMM system from 1.5mm to 0.5mm for benign tumors.

Results: We selected basically 2.7Gy x 10Fr for benign tumors but specially 1.8Gy x 25Fr for recurrent supracellar lesions for preservation of visual functions. All cases are alive and have no neurological deterioration, except only 2 cases of meningioma underwent repeat fractionated radiotherapy.

Conclusions: Although these results are limited to short periods, survival rated, local control rates and qualitative survival rated in patients unsuitable for SRS, such as those with large, recurrent, and eloquent site lesions, were within the acceptable ranges. Further examination is needed for comparison with staged Gamma Knife radiotherapy, Cyber-Knife and Novalis radiotherapies.

 

Takuya KAWABE (Kyoto, JAPAN), Manabu SATO
09:00 - 18:00 #17874 - Frame-based and masked stereotactic radiosurgery: a patient experience comparison with the gamma knife icon.
Frame-based and masked stereotactic radiosurgery: a patient experience comparison with the gamma knife icon.

Introduction

Patients undergoing stereotactic radiosurgery (SRS) for intracranial pathology have two technical treatment options: frame-based versus masked. There is sparse information on a patient’s experience between the two types and to what extent a patient’s diagnosis will predicts their SRS experience.

Methods

A retrospective analysis of patients who completed a questionnaire of their experience of framed-based or masked SRS using the Gamma Knife Icon from June through November 2018 at our institution was completed.

Results

Twenty-eight patients undergoing SRS completed the questionnaire, where 61% of the procedures were frame-based and 39% masked. The average age was 61.2 +16.1 years old, 54% of which were male. Pathologies treated were metastasis, meningiomas, vestibular schwannomas, arteriovenous malformations, neurocytoma, pituitary adenoma, and glioblastoma multiforme. Of the patients treated with a frame-based technique, 59% did not find SRS to be uncomfortable. Comparatively, 82% of patients who received masked treatments did not find SRS to be uncomfortable. Frame-based treatment patients rated their pain of frame placement on a visual analog scale (VAS) 1-3 (24%), VAS 4-6 (48%), VAS 7-10 (24%, one patient didn't rate their pain and was excluded). Five patients answered that they didn't tolerate the procedure as expected. Most of the five patients who perceived not tolerating the procedure, were treated using a framed compared to masked method (80% vs. 20%, respectively). Compared to previous surgery or SRS, 7% found their experience of SRS was not tolerable (both of which were frame-based), while 93% of patients would consider repeat SRS if necessary. All patients who received frame-based and masked treatments felt adequately informed about the procedure. The patient experience of discomfort during SRS was higher with benign versus malignant lesions (63% vs. 20%, respectively). Evaluation of pain during frame placement was similar for patients treated for benign versus malignant lesions (median VAS pain: 6 +1.46 [95% CI 4.9 – 7.1], 4 +2.74 [95% CI 2.2 – 5.8], respectively). 

Conclusions

We found that patient experience undergoing frame-based treatment was less tolerable and caused more discomfort in comparison to the masked technique. Patients experienced more discomfort if they were being treated for a benign compared to a malignant pathology.

Troy DAWLEY, Zaker RANA, Anuj GOENKA, Michael SCHULDER (Lake Success, NY, USA)
09:00 - 18:00 #17840 - Gamma Knife Centre of Queensland: the utility of telehealth services.
Gamma Knife Centre of Queensland: the utility of telehealth services.

Introduction

Telehealth is the process of conducting clinic consultations through a variety of videoconferencing platforms.  The Gamma Knife Centre of Queensland (GKCoQ) was established as a statewide service in October 2015 and has utilized telehealth since January 2016.

The Queensland population is approximately 5 million people but covers a land mass of 1.85million km2, comparable to the area of Mexico.  Given such large geographic regions, gaps in health outcomes have been previously demonstrated between Australian patients from city versus rural/remote areas.  The GKCoQ has sought from its inception to offer an inclusive service for all patients using a telemedicine approach.  Rural and remote patients are able to participate from their homes, local doctors’ rooms, or local Hospital and Health Service telehealth-enabled conference room.

The study aims to examine the workload of the GKCoQ unit, explores the proportion of work streamlined through the telehealth approach, and identifies both barriers and enablers of the telehealth program.

Method

Data regarding the geographic distribution of patients utilizing telehealth was examined retrospectively. New cases and review consultations were included. 

Results

Between January 2016 and January 2019, there were 1359 new patients seen in the Gamma Knife unit in total, and 197 (14%) were seen through the telehealth clinic.  There were 568 telehealth consultations in total and the age of patients ranged from 18 to 88 years.  Most patients seen as a telehealth new case elected to continue to utilize telehealth for follow-up.  17% of telehealth consultations were with Australian patients located outside Queensland, and the vast majority of telehealth patients were from rural areas of Queensland and urban centers outside Brisbane.

Conclusion

The telehealth service is advantageous to the GKCoQ in improving healthcare access to Australians in rural and remote regions, and is an effective means of managing the GKCoQ workload while minimizing patient travel and inconvenience.

Kimberley BUDGEN, Mark PINKHAM, Angela MCBEAN, Natalie CLARKE, Frances WILLIAMS, Anescè STAPELBERG, Bruce HALL, Matthew FOOTE (Brisbane, AUSTRALIA)
09:00 - 18:00 #17835 - Gamma Knife Radiosurgery Strategies for Cystic Lesions and Cyst Formation.
Gamma Knife Radiosurgery Strategies for Cystic Lesions and Cyst Formation.

Introduction: Gamma Knife Radiosurgery (GKR) for cystic-lesion is controversial. Strategies for GKR for these lesions need analyses. The cystic-lesion formation physiopathology is also curious.

Objective: Define strategies of cystic-lesion radiosurgery and mechanisms of cystic lesions after GKR.

Methodology: Analyses of three cases of brain tumors: two with Pilocytic Astrocytoma (PA), one with Pineal Papillary Tumor (PTPR) and cyst formation in an arteriovenous malformation (AVM) treated with embolization and GKR needing microsurgery intervention.

Results: A 9-years-old-girl with PTPR, an 11-year-old boy with PA and a 34-year-old man also with PA had cystic lesions previously submitted to various neurosurgical procedures. They received GKR after stereotactic aspiration and placement of an Ommaya reservoir. Magnetic resonance imaging (MRI) showed remarkable control of the tumors in two of these patients in a bimodal fashion. The 34-year-old patient died due to a sudden cardiac arrest attributed to pulmonary embolism. A 12-year-old boy with a right frontal AVM successfully embolized followed GKR developed after two-years a large cystic lesion occupying the cavity of a pre-treatment bleeding. He required endoscopic ventricular marsupialization and with microsurgery lesion resection.

Conclusion:  Although the present work points out the efficacy of GKR for treatment of PA it is unique for the observation of the bimodal cystic response needing Ommaya reservoir for temporary drainage and the relatively newly described PTPR. The combination of different therapeutic modalities allows for a good quality of life, avoiding multiple large interventions. Cysts secondary to radiosurgery is likely due to edema-induced transudate occupying intra-parenchymal space previously occupied by the treated lesion.

Rafael COSTA LIMA MAIA (São Paulo, BRAZIL), Alessandra GORGULHO, Fabrício CORREA LAMIS, Crystian WILIAN CHAGAS SARAIVA, Antonio DE SALLES
09:00 - 18:00 #17866 - Hypofractionated radiosurgery with Gamma Knife Icon®.
Hypofractionated radiosurgery with Gamma Knife Icon®.

Introduction:

Gamma Knife Radiosurgery (GKRS) yields superior conformity and selectivity. However, large lesions and lesions abutting organs at risk can not be treated safely in a single fraction. To overcome this, one can make use of fractionation. Gamma Knife Icon® with mask immobilization allows to take advantage of (hypo)fractionation in addition to the advantage of its high conformity and selectivity.  In this study, we report on our experience with (hypo)fractionated GKRS.

Material and Methods:

Between January 2016 and November 2018, we have performed 335 Gamma Knife procedures with mask immobilization to treat 83 targets in 73 patients. A dose of 13 to 25 Gy, prescribed to the isodoseline covering 100% of the target, was delivered in 1 to 5 fractions. Fourteen single fraction procedures were performed with mask immobilization because of preferences of the patients. The major indications for fractionation were large volume (43 targets) and or targets abutting cranial nerves (34 targets). Other indications were ill-defined lesions and previous craniotomies. The most common lesions treated were meningioma (43 patients), metastases (26 patients), plexus papilloma (4 patients), vestibular schwannoma (3 patients) and  pituitary adenoma (2 patients). All patients had follow-up in our center with MRI scan as long as clinical meaningful .

Results:

Mean follow-up was 12 months (range 1-31 months). Eight of the 73 patients experienced complications: cranial neuropathy (5 patients), symptomatic edema (2 patients), seizures (1 patient). Twenty-two patients (of which 15 with metastases) died (mean survival 10,2 months, range 2-22,5 months). All patients with a benign disease had local control.

Conclusions:

Gamma Knife Icon® with mask immobilization allows to treat large lesions and lesions abutting organs at risk. It yields high local control rates and minimal toxicity rates. (Hypo)fractionated GKRS can be an alternative to (stereotactic) radiotherapy or to surgery in selected patients.

Patrick HANSSENS, Patrick HANSSENS (Tilburg, THE NETHERLANDS), Guus BEUTE, Suan Te LIE, Jeroen VERHEUL, Bram VAN DER POL, Liselotte LAMERS, Diana GROOTENBOERS, Jannie SCHASFOORT - VAN DEN TILLAART, Wim DE JONG
09:00 - 18:00 #17877 - Primary dose fractionated gamma knife radiosurgery for large volume glomus jugulare tumours.
Primary dose fractionated gamma knife radiosurgery for large volume glomus jugulare tumours.

Objective:Stereotactic radiosurgery is emerging as optimal primary treatment modality for glomus jugulare tumours (GJT). This study evaluates efficacy and safety of dose fractionated gamma knife radiosurgery (DFGKRS) in treatment of glomus jugulare tumours not amenable for single session GKRS.

Material and Methods:Between 2012 and 2017, 10 patients of glomus jugulare tumours were treated with DFGKRS in 2 or 3 sessions. The Leksell G frame was kept in situ during the whole procedure. The tumour volumes on pre- and posttreatment imaging were compared utilizing the Leksell Gamma Plan treatment plan software to assess tumour progression. Pre- and posttreatment symptoms and complications were recorded.

Results: The mean radiological follow up was 39 months. The mean marginal dose for three fractions and two fractions was 7.64 Gy @ 50% and 11.2 Gy @ 50 % respectively. The mean tumour size was 29.9cc at treatment and 21.9cc at follow-up. Tumour control (defined as stable or reduced tumour volume at follow up) was achieved in all patients (100%). Out of 110 potential neurological problems (signs/ symptoms) evaluated (11 in each patient), 56 (50.9%) were present preoperatively. Of them, 27 (48.2%) improved and 29 (51.8%) stabilised after treatment. There were 2 new onset neurological problems (out of 110, 1.8%) attributable to treatment. 

Conclusion:DFGKRS is feasible for glomus jugulare tumours (GJT) with a fair tumour control rate and acceptable toxicity (CTCAE grade 1-2). DFGKRS should be preferred over surgery or radiotherapy in GJT not amenable for single session GKRS.

 

Amanjot KAUR (Mohali, INDIA), Navneet KAUR
09:00 - 18:00 #17711 - Radiosurgery for cranial and spinal haemangioblastomas: monoinstitutional analysis.
Radiosurgery for cranial and spinal haemangioblastomas: monoinstitutional analysis.

PURPOSE. Though primary therapy for Hemangioblastomas (HB) is surgical resection, for patients with subtotally excised or unresectable lesions and for patients with poor clinical status who are not good candidates for surgery, as well as those wishing a minimally invasive approach, radiotherapy (RT) or radiosurgery (SRS) can be an effective alternative. RT and SRS have been associated with good rates of local control in a 60–90% range, especially in patients with VHL. The aim of this study is to evaluate the efficacy and safety of SRS for patients with diagnosis of intracranial and spinal HB in terms of local control and toxicity.

METHODS. We conducted a retrospective analysis of 22 patients with a total of 37 HB: 23 intracranial HB and 14 spinal HB treated at our Institute from January 2012 until February 2017.

A regular clinical and radiological follow-up with MR imaging was scheduled at 4–6 month intervals after SRS procedure. The toxicity was recorded based on CTCAE 3.0v. The radiosurgical procedures were performed using a CyberKnife system, characterized by a 6MV linac mounted on a robotic arm for multiple, non-isocentric, non-coplanar beams sets delivery. Statistical analysis was carried out using SPSS 21.

RESULTS. Twenty-two patients were followed for a median of 42 months (range 3–72 months). Median age at the time of SRS was 44 years (range 19-79), 8 patients were female and 14 male.

The diagnosis of HB was based on the histological findings, except in 7 patients without surgical removal. Seven patients had multiple lesions and 30 patients had a single lesion. The mean prescription dose was 18 Gy (range, 10-25 Gy) in 1-5 fractions with median isodose line of 81% (range, 73-88%).Two patients (9%) developed a recurrence, 12 patients (55%) showed stable disease and 8 (36%) partial response. There was no significant toxicity after treatments.

CONCLUSION. SRS, both in single and multi-fractions settings, is potentially attractive for patients with VHL disease where multiple HB may develop either concurrently or sequentially and may be difficult to treat or retreat with repeated surgery and/or conventional radiation techniques without the risk of toxicity. Our results show that SRS can be considered a safe and effective treatment for intracranial and spinal HB.

Valentina PINZI, Anna VIOLA, Elena DE MARTIN, Cecilia IEZZONI, Marcello MARCHETTI, Laura FARISELLI (milano, ITALY)
09:00 - 18:00 #17651 - Repeat gamma knife radiosurgery for cavernous sinus hemangiomas: a report of 3 cases.
Repeat gamma knife radiosurgery for cavernous sinus hemangiomas: a report of 3 cases.

Background: Gamma knife radiosurgery(GKRS) is well established in the management of cavernous sinus hemangiomas(CaSHs) alternative to microsurgery. Tumor regrowth, however, is occasionally encountered, and treatment modality is usually controversial in such cases. The role of repeat GKRS in these situations is still unclear. The goal of this study was to investigate whether repeat GKRS is an effective and safe treatment for recurrent CaSHs after initial GKRS.Methods: Between January 2008 and November 2009, 42 patients haboring CaSHs were treated using a Leksell Gamma Knife model C at Gamma Knife Center of Huashan Hospital. Of these, 2 patients (4.8%) had regrowth of the residual tumor and 1 patient habored still large volume of tumor after initial GKRS. Repeat GKRS was performed in all three patients, who had more than 100 months of follow-up. There were 2 female and 1 male patients with a median age of 41 (range, 7-54) years old. The median follow-up period after repeat GKRS was 11 months, and the median interval between these interventions was 99 (range, 74-122) months. The median tumor volume was 8.98 and 5.80 ml at the initial and second GKRS treatments, respectively. Patients received a median prescription dose of 13.5 Gy and 14.0 Gy at first and second interventions, respectively.Results: The median follow-up was 110 months (range, 100-128 months). At last follow-up, we report no cases of failure in repeat GKRS for CaSHs. All three patients demonstrated again a significant reduction in tumor volume. The median tumor volume reduction was 65.7% (range, 35.4%-70.1%) and 51.1% (range, 33.2%-53.1%) after initial and repeat GKRS treatments compared with the pre-GKRS volume, respectively. Post-GKRS clinical improvement was achieved in all three patients (100%). No radiation-induced neurological deficits or delayed complications secondary to GKRS were observed during the long follow-up period. Conclusions: This is the first report to address repeat GKRS for CaSHs. Repeat GKRS can result in further tumor volume reduction of residual CaSHs years after initial GKRS. During long-term follow-up, regrowing of remnant CaSHs after GKRS can be detected. Repeat GKRS seems to be a safe and effective treatment in patients harboring regrowth of small CaSHs that have previously been treated with GKRS.

Xuqun TANG (Shanghai, CHINA), Li PAN, Hanfeng WU, Nan ZHANG, Jiazhong DAI
09:00 - 18:00 #17617 - Significance of record maintenance and keeping backups for Radiosurgery patient’s data.
Significance of record maintenance and keeping backups for Radiosurgery patient’s data.

Significance of record maintenance and keeping backups for Radiosurgery patient’s data.

Objective: Radiosurgery patients are generally considered to survive long and quite often require repeat treatment  procedures in future. Therefore, it is highly recommended for centers performing radiosurgery to keep backup strategies in the paced paperless technology era.

Methods: The “Perfexion” Gamma knife unit was installed at PSMMC in Sep. 2013 as the first unit in the kingdom. A total of 110 patients have been treated till October 2018. This unit was installed under the administration of Radiation Oncology department, which requires to keep a record of every radiotherapy treated patient in Varian record and verification system “ARIA” through electronic PDF files of approved radiosurgery plans, alongside a hard copy of documents as conventional manual file of the respective patient. This helps forming a reasonable backup system in case electronic counterpart faces any form of strain.

Unfortunately, on September 2016, an unplanned power shut down led to the permanent damage to the primary hard disc as well as the second backup hard disc, which was physically located at the same premises as the main planning system.

 Despite support team’s utmost efforts, no electronic records could be retrieved.

Results: 67 patients who were treated by Sep. 2016 got all their electronic records lost from the primary server. The only available information was based on the “ARIA”  which saved it from this unprecedented event. In order to identify targets and their formations, a procedure was adopted to extract information from shots configurations based on records in the later. Clinical records were extracted back from the prospective database collected upon the manual traditional files.

Conclusion: It is highly recommended to keep a scientific base as a backup strategy for radiosurgery data which can disappear in an extraordinary state.

Bilal MUHAMMAD, Marouf ADILI (Riyadh, SAUDI ARABIA), Saleh BAMAJBOUR, Abdulaziz ALHAMAD
09:00 - 18:00 #17656 - The imaging cost of matching the treatment accuracy between frame and frameless stereotactic linac radiosurgery.
The imaging cost of matching the treatment accuracy between frame and frameless stereotactic linac radiosurgery.

Objective:To compare the intrafraction motion and the setup imaging time between 2 cohorts of patients (frame-based and frameless) treated with linac stereotactic radiosurgery at Tom Baker Cancer Centre.

 Methods:We conducted a retrospective single-institution review of 40 patients treated in a single fraction with linac stereotactic radiosurgery. Twenty patients were immobilized using the Brainlab frame system (Brainlab Munich, Germany) and 20 patients were immobilized using the open face mask Orfit system (Orfit Industries, Wijnegem, Belgium). Initial setup for each patient was completed by acquiring a cone beam CT (CBCT) and an automatic match until shifts and rotations were within our 0.5mm and 0.3° tolerances. A CBCT and automatic match was also performed between each arc to determine the intrafraction motion. Additional CBCTs required to meet the matching tolerance level were also acquired and shifts were recorded for both cohorts, and this was used to calculate the extra time taken for treatment.  

 Results:The mean shifts and rotations (± one standard deviation) between the 2 cohorts (framed and frameless respectively) were -0.1±0.1 mm and 0.0±0.2 mm (vertical), 0.0±0.1 mm and 0.0±0.2 mm (lateral), 0.0±0.1 mm and 0.0±0.3 mm (longitudinal), 0.0±0.1 ° and 0.1±0.3 ° (pitch), 0.0±0.1 ° and 0.0±0.1 ° (roll), 0.0±0.1 ° and 0.0±0.2 ° (yaw). An unpaired t-test showed there was no significant difference in the shifts and the rotations between the two immobilization systems. An average of 0.2 and 1.4 additional CBCT scans per isocentre were required for framed and frameless treatments, respectively, for patients to be within match tolerances for treatment.  This translates to an average increase in treatment time of 1.2 min (framed) and 8.4 min (frameless) using 6 min as the average time for acquiring, matching and applying moves per CBCT at our institution.

 Conclusion:The same level of geometrical accuracy can be achieved with either framed or frameless immobilization. This accuracy comes at the cost of extra imaging time, which is significantly higher for frameless SRS. The number of additional scans required for framed patients suggests that CBCT in between arcs may not be necessary; however, CBCT between arcs is essential for frameless patients to achieve the desired accuracy in SRS due to increased intrafraction motion with this form of immobilization.

Nicolas P PLOQUIN (Calgary, CANADA), Alana HUDSON, Gerald LIM, Shaun LOEWEN, Salman FARUQI
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P17
09:00 - 18:00

EPOSTER - 17 ocular
Electronic Poster displayed from June 9 to June 13

09:00 - 18:00 #16744 - RADIATION MACULOPATHY AFTER ONE-DAY SESSION STEREOTACTIC RADIOSURGERY IN PATIENTS WITH UVEAL MELANOMA.
RADIATION MACULOPATHY AFTER ONE-DAY SESSION STEREOTACTIC RADIOSURGERY IN PATIENTS WITH UVEAL MELANOMA.

INTRODUCTION: Radiotherapy/surgery (SRS) is the standard treatment care for patients with uveal melanoma. In Slovakia we use one-day session stereotactic radiosurgery at linear accelerator C LINAC. One of the most serious and vision-threatening complications after SRS is the radiation retinopathy, which divides into maculopathy and peripheric retinopathy. The clinical signs include microanerysms, teleangiectases, hard exsudates, cotton wool spots and macular edema, neovascularisation, and vitreous hemorrhage . Radiation macular edema can be classified by optical coherence tomography into cystoid or noncystoid edema.
MATERIAL AND METHODS: The retrospective analysis of maculopathy in a group of 168 patients with uveal melanoma after one-day session stereotactic radiosurgery on linear accelerator C LINAC in a period 2007-2016.
RESULTS: Therapeutic dose to the tumor was 35.0Gy. The prevalence of the radiation maculopathy was 29% with the median time from the irradiation to maculopathy in 16 months. Median radiation dose on the macula was 37.0 Gy. Variables statistically significantly associated with the maculopathy were: radiation dose (p=0.0016), postequatorial location of the tumor (p=0.0271), tumor touch of the macula and better visual acuity before treatment (p=0.00076). The tumor touch of the macula was strongly associated with the visual acuity loss (bivariate analysis -p=0.0006).

Five patients underwent intravitreal application of the bevacizumab as a treatment of the radiation maculopathy, without improvement of the visual acuity.


The radiation dose on a macula is the key determinant for radiation-induced maculopathy, other variables were related to distance of the tumour to the macula, so the radiation dose on the macula was higher indirectly. Better visual acuity before treatment as a risk factor for maculopathy can be a consequence of a) earlier diagnostics of tumor with proximity to the posterior pole (uveal melanoma stage T1) b) frequency of the secondary enucleation afetr SRS was 1.6 times higher in patients without maculopathy (uveal melanoma stage T2-T3 tumors) 

CONCLUSION: Radiation complications can lead to visual acuity loss and secondary enucleation. Radiation maculopathy is a consequence of higher radiation dose to the macula. The treatment modalities of radiation maculopathy are rather ineffective.

Alena FURDOVA (Bratislava SLOVAKIA, SLOVAKIA), Iveta WACZULIKOVA, Miron SRAMKA, Gabriel KRALIK, Martin CHORVATH
09:00 - 18:00 #17756 - Stereotactic radiosurgery (SRS) in choroidal melanoma: experience and cost efficiency.
Stereotactic radiosurgery (SRS) in choroidal melanoma: experience and cost efficiency.

Objectives

To analyze local control (LC), disease free survival, toxicity and cost effectiveness of SRS treatment of choroidal melanoma.

 

Material and methods

Between 2003 and 2017, 7 patients with choroidal melanoma were treated in a private hospital in Spain. Mean age at diagnosis was 60 years (43-79 years). The mean tumor volume was 0.49 cm3 (0.13-0.93) and distant disease was ruled out.

The first step is to fix the ocular rectus muscles at the Leksell frame doing a retrobulbar blockage with local anesthesia. The delineation of the tumor was made by fusion of magnetic resonance (MRI) and computerized tomography (CT) in stereotactic conditions. The minimum marginal dose administered was 35 Gy in a single session. The treatment is with a linear accelerator (LINAC) with cones. It is an outpatient procedure with estimate duration of 3 hours. The overall cost of the procedure is around $-9,000, compared to $-16,125 of brachytherapy.

 

Results

Mean follow up of 64 months (13-186), 100% local control rate has been reached without any enucleation. One patient developed distant disease (hepatic metastasis) one year after SRS. MRI complete radiological response was observed in two patients, three had maximum partial response (≥ 50%) and two a minor partial response (≤ 50%). The maximum dose in crystalline was 13.63 Gy and 27.9 Gy in optic nerve.  Follow-up, one of the patients required cataract surgery, another had retinal detachment 5 years latter and posterior macular edema with a significant decrease in visual acuity. Neovascular glaucoma presented 9 months after SRS in a patient with a previous cataract surgery, improved after intravitreal antiangiogenics.

 

 

 

Discussion

SRS is safe with acceptable toxicity. Survival and LC is equivalent to other techniques, is a cost efficiency procedure, alternative to enucleation and brachytherapy, that allows the treatment of larger tumors and close to the optic nerve.

Luis LARREA (Valencia, SPAIN), Enrique LOPEZ-MUNOZ, Veronica GONZALEZ, Paola ANTONINI, Maria BANOS-CAPILLA, Jose BEA-GILABERT
09:00 - 18:00 #17779 - The first application of gamma-knife radiosurgery for diffuse choroidal hemangioma in a patient with Sturge-Weber syndrome.
The first application of gamma-knife radiosurgery for diffuse choroidal hemangioma in a patient with Sturge-Weber syndrome.

Purpose: to present a case of successful Gamma-knife radiosurgery (GKRS) of the single eye with diffuse choroidal hemangioma (DCH) in a child with Sturge-Weber syndrome.

Methods: A 4.5-year old girl was referred to our center with port-wine stains of the face, leptomeningeal angiomas and bilateral DCH. The right eye was presented with DCH of 6.6 mm in thickness with no signs of exudation.

The left eye was diagnosed with DCH of 6.8 mm in thickness, total retinal detachment and vision loss. Ruthenium brachytherapy was performed but retinal detachment increased.

Within 5 months follow-up the right eye developed retinal detachment up to 6.6 mm in height. GKRS was used as the last opportunity to save the eye and improve vision. Dosimetric plan included double PTVs of 18 Gy @ 57% and 18 Gy @ 50% excluding central retina, and will be presented.

Results: During 8 months of follow up choroidal tumor thickness decreased from 6.6mm to 3.0mm with retinal detachment resolution that provided child a good vision in the only seeing eye. Irradiation “tracks” according to the planning were seen on the eye fundus examination without radiation damage of central retina. No complications were revealed within the follow-up.

Conclusion: This exceptional case presents the first to our knowledge experience of GKRS of DCH in a child with Sturge-Weber syndrome. GKRS allowed to irradiate intraocular vascular tumor precisely and save the eye with vision improvement. Further experience is essential.

Andrey YAROVOY (Moscow, RUSSIA), Andrey GOLANOV , Roman LOGINOV, Vera YAROVAYA, Valery KOSTJUCHENKO, Amina CHOCHAEVA
Sunday 09 June
08:00

Sunday 09 June

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B11
08:00 - 10:00

ISRS SRS/SBRT EDUCATIONAL COURSE
INTRACRANIAL SRS: THE BASICS

Moderators: Guilherme ESPOSITO QUERELLI (Physicist) (Brasília, BRAZIL), Matthew FOOTE (Co-Director) (Brisbane, AUSTRALIA), Crystian SARAIVA (Medical Physicist) (São Paulo, BRAZIL)
08:00 - 08:10 Introduction & Course Objectives. Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL)
08:10 - 08:30 Principles of Radiosurgery. Laura FARISELLI (director) (milano, ITALY)
08:30 - 08:50 Radiobiology of Radiosurgery. Dennis SHRIEVE (Professor and Chair) (Salt Lake City, USA)
08:50 - 09:10 QA and Imaging. Ian PADDICK (Physicist) (London, UK)
09:10 - 09:30 Imaging for Radiosurgery. Stephen HOLMES (Imaging Consustant and Conference Organizer) (honolulu, USA)
09:00 - 10:00 Discussion.
Segovia Break Out
10:00 COFFEE BREAK Segovia Break Out
10:20

Sunday 09 June

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B13
10:20 - 12:00

ISRS SRS/SBRT EDUCATIONAL COURSE
INTRACRANIAL SRS: CLINICAL INDICATIONS

Moderators: Julio ANTICO (ARGENTINA), John SUH (Radiation Oncologist) (Cleveland, USA), Paul W. SPERDUTO (2HBK7YS$) (Minneapolis, USA)
10:20 - 10:40 Brain Metastases. Patrick HANSSENS (Radiation Oncologist) (Tilburg, THE NETHERLANDS)
10:40 - 11:00 Brain Protection with Repeat SRS : Making Whole Brain Radiation Obsolete. Iris GIBBS (Professor) (Stanford, USA)
11:00 - 11:20 Intracranial Benign Lesions. Samuel CHAO (Radiation Oncologist) (Cleveland, USA)
11:20 - 11:40 Stereotactic Radiosurgery for AVMs. Bruce POLLOCK (Physician) (Rochester, USA)
11:40 - 12:00 Trigeminal Neuralgia and Functional Disorders. Alessandra GORGULHO (Director of Research Affairs) (Sao Paulo, BRAZIL)
Segovia Break Out
12:00 LUNCH - Oceanico's Restaurant Segovia Break Out
13:00

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B15
13:00 - 14:30

ISRS SRS/SBRT EDUCATIONAL COURSE
SBRT: THE BASICS

Moderators: Francine Xavier DOS SANTOS (Medical Physicist) (porto alegre, BRAZIL), Uriel NOVICK (Chief Medical Physicist) (CABA, ARGENTINA), Marta SCORSETTI (Director Department) (Rozzano-Milan, ITALY)
13:00 - 13:20 Contouring. Caroline CHUNG (Associate Professor, Radiation Oncology) (Houston, USA)
13:20 - 13:40 Treatment planning considerations for SBRT: from optimization to dose calculation. Andrea GIRARDI (Medical Physicist) (Brussels, BELGIUM)
13:40 - 14:00 Immobilization and Positioning Considerations. Paul MEDIN (Radiation Oncology) (Dallas, USA)
14:00 - 14:20 Motion Management Techniques. Fang-Fang YIN (Medical Physicist/Professor) (Durham, NC, USA)
14:20 - 14:30 Discussion.
Segovia Break Out

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C15
13:00 - 14:30

LGKS AFTERNOON SESSION - Part I
Radiosurgery - What we can expect in the future?

13:00 - 13:05 Welcome. Dan LEKSELL (Chairman) (Stockholm, SWEDEN)
13:05 - 13:30 Personalized machine learning - AI based segmentation & plan generation. Kenneth LAU (Stockholm, SWEDEN)
13:30 - 14:00 Sunnybrook approach to multiple metastases – SPARE technique and workflow. Arjun SAHGAL (Professor) (Toronto, CANADA)
14:00 - 14:30 Radiosurgery & Immunotherapy--A Good Bet? Jonathan KNISELY (Lake Success, USA)
El Pardo I
14:30 COFFEE BREAK Segovia Break Out
14:50

Sunday 09 June

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C17
14:50 - 18:00

LGKS AFTERNOON SESSION - Part II
Radiosurgery - What we can expect in the future?

14:50 - 15:20 Increased visualization in CBCT imaging – How far can we get? Kenneth LAU (Stockholm, SWEDEN)
15:20 - 15:50 MR guided RT with Unity – Potential applications and benefits. Caroline CHUNG (Associate Professor, Radiation Oncology) (Houston, USA)
15:05 - 16:10 Foresee outcome using pathology, blood biomarkers, genomics & radiomics. Hakan NORDSTROM (Physicist) (Stockholm, SWEDEN)
16:10 - 16:40 Radiosurgery for OCD and major depression. Antonio Carlos LOPES (Collaborating Professor) (São Paulo, BRAZIL)
16:40 - 17:10 What can we learn from dose planning comparison studies? Ian PADDICK (Physicist) (London, UK)
17:10 - 17:20 Next generation inverse planner. Bjorn SOMELL (Product Manager Treatment Planning) (Stockholm, SWEDEN)
17:20 - 17:30 Intuitive interactive inverse planning for Gamma Knife radiosurgery. Marc LEVIVIER (Chef de Service) (Lausanne, SWITZERLAND)
17:30 - 17:55 Fast and comprehensive plan adaptation. Hakan NORDSTROM (Physicist) (Stockholm, SWEDEN)
17:55 - 18:00 Concluding remarks. Dan LEKSELL (Chairman) (Stockholm, SWEDEN)
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B17
14:50 - 17:00

ISRS SRS/SBRT EDUCATIONAL COURSE
SBRT: CLINICAL INDICATIONS

Moderators: Laura FARISELLI (director) (milano, ITALY), Samuel RYU (Professor) (Stony Brookn NY, USA), Kita SALLABANDA (Asoc.Prof.) (Madrid, SPAIN)
14:50 - 15:10 Lung. Ben SLOTMAN (Professor and Chairman) (AMSTERDAM, THE NETHERLANDS)
15:10 - 15:30 The evolving role of SBRT in the management of liver metastases. Marta SCORSETTI (Director Department) (Rozzano-Milan, ITALY)
15:30 - 15:50 Prostate SBRT. Patrick KUPELIAN (Professor) (Palo Alto, USA)
15:50 - 16:10 Spine. Arjun SAHGAL (Professor) (Toronto, CANADA)
16:10 - 16:30 Oligometastases. Rupesh KOTECHA (Radiation Oncologist and Chief of Radiosurgery) (Miami, USA)
16:30 - 16:50 Other and Emerging Indications. Lauren HENKE (Radiation Oncologist) (St. Louis, USA)
16:50 - 17:00 Discussion.
Segovia Break Out
18:00

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A18
18:00 - 19:00

OPENING LECTURES

18:00 - 18:05 Welcome By Antonio De Salles and Brazil-Latin American Presentation Congress Chairman. Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL)
18:05 - 18:25 Welcome and Lecture from Ministry of Science, Technology, Innovation and Communications - MCTIC. Marcello MORALES (Brasilia, BRAZIL)
18:00 - 19:00 Define your Brand. Edmour SAIANI (BRAZIL)
18:00 - 19:00 Words of Welcome. Ian PADDICK (Physicist) (London, UK)
18:00 - 19:00 Words of Logistics. Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL)
Segovia Plenary
19:00 OPENING RECEPTION - EXHIBITION AREA
Monday 10 June
07:30

Monday 10 June

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A21
07:30 - 09:00

BREAKFAST SEMINAR
ISRS GUIDELINES OVERVIEW

Moderators: Randy JENSEN (Professor) (Salt Lake City, USA), Daniel PAZ (BRAZIL), Arjun SAHGAL (Professor) (Toronto, CANADA)
07:30 - 07:40 ISRS Guidelines for Multiple Brain Metastases. Steve BRAUNSTEIN (Faculty) (San Francisco, USA)
Antonio DE SALLES, Laura FARISELLI, Marc LEVIVIER, Ian PADDICK, Bruce POLLOCK, Jean REGIS, Jason SHEEHAN, John SUH, Shoji YOMO, Lijun Ma
07:40 - 07:50 Technological Considerations for Small Brain Metastases. Alexis DIMITRIADIS (Physicist) (London, UK)
Antonio DE SALLES, Laura FARISELLI, Marc LEVIVIER, Lijun MA, Bruce POLLOCK, Jean REGIS, Jason SHEEHAN, John SUH, Shoji YOMO, Ian Paddick
07:50 - 08:00 #17901 - Stereotactic radiosurgery for post-operative metastatic surgical cavities : International Society of Stereotactic Radiosurgery (ISRS) practice guideline.
Stereotactic radiosurgery for post-operative metastatic surgical cavities : International Society of Stereotactic Radiosurgery (ISRS) practice guideline.

The historical standard of care in patients who have undergone surgical resection of brain metastases is whole brain radiation therapy (WBRT) based on data that resection alone is associated with high rates of local recurrence.  Unfortunately, WBRT is associated with long term cognitive toxicity and as such SRS to the resection cavity has been increasingly utilized.  As part of the ISRS Guideline Committee, the purpose of this project is to summarize the current literature for stereotactic radiosurgery (SRS) for post-operative brain metastases resection cavities.  Medline and Embase databases were utilized to search for manuscripts reporting outcomes following SRS for post-operative brain metastases tumor bed resection cavities with a search end date of July 20, 2018.  Prospective studies, consensus guidelines, and retrospective series that included exclusively post-operative brain metastases, had at minimum 100 patients were considered eligible. Embase search revealed a total of 157 manuscripts of which 77 were selected for full text screening. Pubmed search revealed a total of 55 manuscripts of which 23 were selected for full text screening.  After excluding articles that did not meet eligibility criteria or present data specific for resection cavity SRS as well as eliminating duplicates, a total of 12 articles were deemed appropriate for inclusion.  Specifically, results of 9 retrospective series, a single phase II prospective study, 3 randomized controlled trials, and a consensus contouring manuscript were included.  Overall, these data suggest that SRS to brain metastases resection cavities is associated with excellent local control as high as 91%.  Randomized data suggests improved local control with SRS compared to observation and improved cognitive outcomes compared to WBRT.  Toxicity of SRS in the post-operative setting were limited, although development of leptomeningeal disease was reported to be higher than 10% in the 5 studies in which it was investigated.  To conclude,  SRS for post-operative brain metastases resection cavities demonstrates excellent local control and low toxicity.  Future investigations aiming to reduce the risk of leptomeningeal disease will be important. 

Kristin REDMOND (Baltimore, MD, USA), Arjun SAHGAL
08:00 - 08:10 #17541 - Stereotactic radiosurgery for post-operative spinal metastases: International Society of Stereotactic Radiosurgery (ISRS) practice guideline.
Stereotactic radiosurgery for post-operative spinal metastases: International Society of Stereotactic Radiosurgery (ISRS) practice guideline.

Objective: Spine stereotactic body radiation therapy (SBRT) is increasingly utilized as a treatment option for patients after surgery for spinal metastatic disease. The purpose of this review was to determine the efficacy and toxicity of spine SBRT post-operatively as well as to determine the surgical and radiosurgical techniques most commonly reported in the literature.

Methods: A systematic literature review was conducted using PubMed and Embase according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Keywords used included “postoperative spine radiosurgery”, “postoperative spine SBRT”, “postoperative spine stereotactic body radiotherapy” and “postoperative spine stereotactic body radiation therapy”.

Results: A total of 557 articles were identified, of which 54 were selected for in-depth review. 18 publications met all of the inclusion criteria of which 8 were retrospective, 4 were retrospective of prospective databases, 3 were prospective, 2 were phase I/II studies and 1 had a mixed design of phase I/II study and retrospective patients. A total of 665 spinal segments were treated across these studies. In the 9 studies that reported it 1yr local control ranged from 70% to 100%. 13 studies commented on toxicity and only one patient was documented with myelopathy of a previously irradiated spinal segment retreated with post-operative spine SBRT. Guidelines based on this systematic review are in development.

Conclusion: Spine SBRT is a safe and effective treatment option for patients post-surgery and can be considered in select cases based on mostly low-quality data.

Salman FARUQI (Calgary, CANADA), Arjun SAHGAL, Laura FARISELLI, Marc LEVIVIER, Lijun MA, Ian PADDICK, Bruce POLLOCK, Jean RÉGIS, Jason SHEEHAN, John SUH, Shoji YOMO, Antonio DE SALLES
08:10 - 08:20 #17635 - a21-5 Stereotactic Radiosurgery for Spetzler Grade I and II AVM: Systematic Review for the Formation of International Society of Stereotactic Radiosurgery (ISRS) Practice Guideline.
Stereotactic Radiosurgery for Spetzler Grade I and II AVM: Systematic Review for the Formation of International Society of Stereotactic Radiosurgery (ISRS) Practice Guideline.

Background: The role of stereotactic radiosurgery (SRS) in the management of Spetzler-Martin Grade I and II arteriovenous malformations (AVM) is controversial, with no consensus guidelines available to inform treatment recommendations.

Objective: Systematic literature review for development of objective SRS practice guidelines.

Methods: Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were employed. We searched Medline, Embase, and Scopus, 1986-2018, identifying English language publications reporting post-SRS outcomes in ≥10 Grade I-II patients with median follow-up ≥24 months. Primary endpoints were AVM obliteration and hemorrhage; publications not reporting both were excluded. Initial search identified 447 candidate records; 71 underwent full-text screening; 8 publications reporting 1102 patients were included.

Results: Of 1102 AVM, 836 were Grade II. Obliteration was achieved in 884 (80%) at a median 37 months; 66 hemorrhages (6%) occurred during a median follow-up of 68 months. Excellent outcomes were achieved in 743 of 952 patients with requisite data reported (78%). Among 680 Grade II lesions with Spetzler-Martin parameters reported, 377 were located in eloquent brain, and 178 had deep venous drainage, indicating that 82% of Grade II AVM treated with SRS had a high risk feature.

Conclusions: SRS is a safe, effective treatment for Spetzler-Martin Grade I-II AVM, and should be considered front-line for many low-grade AVM—in particular, those with eloquent location or deep venous drainage. Systematic selection bias appears to have influenced referral patterns, with favorable AVM typically recommended for resection, while lesions that carry a higher resection risk—and a lower probability of obliteration—are disproportionately referred for SRS.

Christopher GRAFFEO (Rochester, MN, USA), Arjun SAHGAL, Antonio DE SALLES, Laura FARISELLI, Marc LEVIVIER, Lijun MA, Ian PADDICK, Jean REGIS, Jason SHEEHAN, John SUH, Shoji YOMO, Bruce POLLOCK
08:20 - 08:30 #17639 - Stereotactic radiosurgery for non-functioning pituitary adenomas: International Society of Stereotactic Radiosurgery (ISRS) practice guideline.
Stereotactic radiosurgery for non-functioning pituitary adenomas: International Society of Stereotactic Radiosurgery (ISRS) practice guideline.

Purpose/Objectives: Stereotactic radiosurgery (SRS) has become an established treatment for patients with non-functioning pituitary adenomas (NFAs) in the definitive, adjuvant, or recurrent setting. This review of the published literature regarding patient selection, dose and fractionation, and treatment-related outcomes and toxicities was performed to develop consensus guidelines. 

 

Materials/Methods: Using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, a systematic review of the published English literature was performed using articles describing clinical outcomes of at least 10 patients with NFAs published prior to May 2018 using the Medline database and the following key words: “radiosurgery” and “pituitary” and/or “adenoma.”

 

Results: Of the 678 abstracts reviewed, a total of 35 full-text articles were included in this analysis describing the clinical outcomes of 2671 patients treated between 1971-2017. All included studies were retrospective. A majority of patients had undergone surgery (Median: 95%, Range: 0-100%) prior to SRS, and a small proportion had received prior radiotherapy (Range: 0-17%). The median tumor volume at the time of SRS was 3.5 cc. Single fraction treatment was used in 27 studies (Median dose: 15 Gy, Range: 5-35 Gy) and hypofractionated treatments were used in 8 studies (Median total dose: 21 Gy, Range: 12-25 Gy delivered in 3-5 fractions). Tumor control was favorable across studies (Range: 90-100%). Post-treatment hypopituitarism was the most common treatment-related toxicity observed (Range: 0-32%), whereas visual dysfunction or cranial nerve injury rarely occurred (Range: 0-7%).

 

Conclusions: Based on these retrospective studies, practice guidelines were developed with consensus from the International Stereotactic Radiosurgery Society. We conclude SRS is an effective treatment option for patients with NFAs with limited treatment-related toxicities.

Rupesh KOTECHA (Miami, USA), Arjun SAHGAL, Antonio DE SALLES , Laura FARISELLI, Bruce POLLOCK, Marc LEVIVIER, Lijun MA, Ian PADDICK, Jean REGIS, Jason SHEEHAN, Shoji YOMO, John SUH
08:30 - 08:40 #17725 - a21-4 Stereotactic radiosurgery for secretory pituitary adenomas: systematic review and development of ISRS guidelines.
Stereotactic radiosurgery for secretory pituitary adenomas: systematic review and development of ISRS guidelines.

A systematic review was performed to provide objective evidence on the use of stereotactic radiosurgery in the management of secretory pituitary adenomas and develop consensus guidelines recommendations.

The authors performed a systematic review of English-language literature up until June 2018 using the Pubmed, Medline, Embase and Cochrane databases. The following MeSH terms were used to search for relevant articles: (Gamma Knife OR Radiosurgery OR LINAC OR Cyberknife) AND (pituitary adenoma OR Cushing’s disease OR acromegaly OR prolactinoma). The initial search provided 1045 articles whose title and abstract were screened, retaining 134 articles. Full text screening of those articles was performed, using the following inclusion criteria: single institution study, more than 10 patients reported, both tumor and endocrine control data reported. Proton SRS, FSRT and studies only reporting Nelson syndromes were excluded. In cases of multiple studies from the same institution, only the most recent was included. 

A total of 49 articles were selected for the analysis. All studies were retrospective case series. Many studies reported the outcomes of all pituitary adenomas treated at that institution. From those, only the data reporting the outcomes of Cushing’s disease, acromegaly or prolactinoma was extracted.

Data analysis is ongoing at the moment and will be completed at the time of the meeting.

David MATHIEU (Sherbrooke, CANADA)
08:40 - 08:50 #16742 - Stereotactic radiosurgery for intracranial, non-cavernous sinus, benign meningiomas: international society of stereotactic radiosurgery (isrs), practice guideline.
Stereotactic radiosurgery for intracranial, non-cavernous sinus, benign meningiomas: international society of stereotactic radiosurgery (isrs), practice guideline.

Objective. Radiosurgery (RS) for benign intracranial meningiomas is increasingly being used. Considering this, the aim of the present review is to define practice guidelines to support the clinicians in the radiosurgical management of such lesions.

Methods. Articles published from January 1964 to April 2018 were systemically reviewed. Three electronic databases, PubMed, EMBASE, and The Cochrane Central Register were searched. Publications in English about benign meningiomas’ radiosurgery.

Results. Of 2844 studies, 306 studies had a full text evaluation and 42 studies met the above mentioned criteria and were then include in the present analysis. All but two are retrospective studies. The 10 local control (LC) range from 85 to 100%. The ten years progression free survival (PFS) range from 52 to 97 %. The median post-RS symptoms worsening rate is near 9 %. The most common treatment dose range from 12 to 15 Gy delivered in a single fraction.

Conclusions. The current literature lacks of level I and II evidences. Despite this, due to the large consensus of level III evidences, sRS represents an effective treatment paradigm for benign intracranial meningioma (recommendation level II). The ideal treatment time has to be better investigated as well as the potential advantages of the mRS.

Marcello MARCHETTI (Milano, ITALY), Arjun SAHGAL, Antonio DE SALLES, Marc LEVIVIER, Lijun MA, Ian PADDICK, Bruce POLLOCK, Jean REGIS, Jason SHEEHAN, John SUH, Shoji YOMO, Laura FARISELLI
Segovia Plenary

Monday 10 June

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B21
07:30 - 09:00

BREAKFAST SEMINAR
SBRT IN OPERABLE LUNG

Moderators: Hilde KLEIVEN (radiation oncologist) (Canberra, AUSTRALIA), Patrick KUPELIAN (Professor) (Palo Alto, USA), Lisa MORIKAWA (BRAZIL)
07:30 - 07:48 Patient Selection. Simon CHENG (Assistant Professor) (New York, USA)
07:48 - 08:06 Motion Management. Anderson PASSARO (Medical Physicist) (São Paulo, BRAZIL)
08:06 - 08:24 Evidence Review. Jin Ho KIM (Associate Clinical Professor) (Seoul, KOREA)
08:24 - 08:42 Resection of Thoracic Metastases. Rui HADDAD (BRAZIL)
08:42 - 09:00 MR Guided SBRT for Lung Tumors. Ben SLOTMAN (Professor and Chairman) (AMSTERDAM, THE NETHERLANDS)
Segovia Break Out

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C21
07:30 - 09:00

BREAKFAST SEMINAR
MACHINE LEARNING AND AI IN SRS/SBRT

Moderators: Guilherme BULGRAEN DOS SANTOS (BRAZIL), Renan SERRANO RAMOS (BRAZIL), Fang-Fang YIN (Medical Physicist/Professor) (Durham, NC, USA)
07:30 - 07:52 The Potential of AI in SBRT. Fang-Fang YIN (Medical Physicist/Professor) (Durham, NC, USA)
07:52 - 08:14 Inverse Treatment Planning. Marc LEVIVIER (Chef de Service) (Lausanne, SWITZERLAND)
08:14 - 08:36 Dose Painting/Delivery Automation. Richard POPPLE (Medical Physicist) (Birmingham, USA)
08:36 - 09:00 Automatic Segmentation of Structures in the Brain. Crystian SARAIVA (Medical Physicist) (São Paulo, BRAZIL)
El Pardo I
09:00

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A21b
09:00 - 09:05

OPENING ADDRESS

Speakers: Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL), Ian PADDICK (Physicist) (London, UK)
Segovia Plenary
09:05

Monday 10 June

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A22
09:05 - 10:20

PLENARY SESSION
WHAT IS REALLY HAPPENING WHEN WE TREAT?

Moderators: Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL), John KIRKPATRICK (Professor - Radiation Oncology & Neurosurgey) (Durham, NC, USA), Ian PADDICK (Physicist) (London, UK)
09:05 - 09:20 #17820 - A22-1 Basic radiobiology of high-dose SBRT and SRS.
Basic radiobiology of high-dose SBRT and SRS.

We have observed that, in experimental tumors, significant additional tumor cell death occurs during several days after irradiation with >10 Gy, most likely due to the radiation-induced vascular destruction. We then found that treating the host animals with hypoxic cytotoxins, such as PR-104, further increases death or residual hypoxic cells. We recently observed that fractions of the surviving hypoxic cells in tumors after 10-20 Gy irradiations undergo reoxygenation in 2-5 days. It appeared that the oxygen supply via a small proportion of blood vessels that escaped total occlusion by irradiation together with the significant decrease in oxygen consumption induced the reoxygenation of hypoxic tumor cells. In recent years, numerous reports indicated that high-dose irradiation evoked anti-tumor immunity by increasing the cytotoxic T-cell population, and that inhibition of anti-immune checkpoints such as PD-L1 and PD-1 improved the anti-cancer immunity.  On the other hand, in our recent study, high-dose irradiation significantly upregulated HIF-1α and increased the anti- immune PD-L1 and PD-1. It has been known that HIF-1α directly controls the PD-L1: PD-1 axis. We have previously reported that anti-diabetes drug metformin effectively suppressed  the radiation-induced upregulation of  HIF-1α. Together, it appeared that HIF-1 α inhibitors such as metformin may block the radiation-induced upregulation of the anti-immune PD-L1: PD-1 axis thereby they increase the antitumor immunity.

In summary, (i) Additional tumor cell death due to vascular injury plays an important role in the response of tumors to high-dose SBRT/SRS. (ii) The efficacy of SBRT/SRS may be markedly improved by increasing the post-irradiation death of hypoxic cells with hypoxia cytotoxin. (iii) Allowing 2-5 days between irradiations in fractionated SBRT/SRS may render hypoxic tumor cells reoxygenated. (iii) Suppressing the radiation-induced upregulation of PD-L1: PD1 axis using HIF-1α inhibitors may significantly improve the anti-cancer immunity after SRRT/SRS.  

Chang SONG (Minneapolis, USA), Kathryn E. DUSENBERY, Stephanie TEREZAKIS, L. Chinsoo CHO
09:20 - 09:35 The Concept of BED in SRS. John HOPEWELL (invited speaker) (Oxford, UK)
09:35 - 09:50 Can Radiobiology help us further refine SRS treatments? John KIRKPATRICK (Professor - Radiation Oncology & Neurosurgey) (Durham, NC, USA)
09:50 - 10:05 Imaging of Radiation Necrosis. Yael MARDOR (Research) (Ramat-Gan, ISRAEL)
10:05 - 10:20 Oncogenesis & Stereotactic Radiation: What We Know. Jonathan KNISELY (Lake Success, USA)
Segovia Plenary
10:20 COFFEE BREAK - POSTERS & EXHIBITION
10:45

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A24
10:45 - 12:00

PARALLEL SESSION
MR GUIDED SRS/SBRT: CURRENT STATE & FUTURE DIRECTIONS

Moderators: John ADLER (neurosurgery) (Région de la baie de San Francisco, USA), Patrick KUPELIAN (Professor) (Palo Alto, USA), Ben SLOTMAN (Professor and Chairman) (AMSTERDAM, THE NETHERLANDS)
10:45 - 11:00 MR GUIDED SRS/SBRT: Technical Overview. Ben SLOTMAN (Professor and Chairman) (AMSTERDAM, THE NETHERLANDS)
11:00 - 11:15 Realtime Adaptive Therapy: Workflow Considerations. Frank LAGERWAARD (Radiation Oncologist) (Amsterdam, THE NETHERLANDS)
11:15 - 11:30 Beyond Anatomical Imaging: The Promise and Challenges. Caroline CHUNG (Associate Professor, Radiation Oncology) (Houston, USA)
11:30 - 11:45 Clinical Indications & Results. Lauren HENKE (Radiation Oncologist) (St. Louis, USA)
11:45 - 12:00 Clinical Trials and Research Overview. Arjun SAHGAL (Professor) (Toronto, CANADA)
Segovia Plenary

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B24
10:45 - 12:00

Oral Session
FUNCTIONAL #1 - OCD/PAIN

Moderators: Eduardo ALHO (Neurosurgeon) (São Paulo, BRAZIL), Carlos CIAROLO (ARGENTINA), Jean REGIS (PROFESSEUR) (MARSEILLE, FRANCE)
10:45 - 10:55 #17863 - b24-1 Deterministic Diffusion Tensor Imaging Tractography and Gamma Ventral Capsulotomy for Obsessive-compulsive disorder.
b24-1 Deterministic Diffusion Tensor Imaging Tractography and Gamma Ventral Capsulotomy for Obsessive-compulsive disorder.

BACKGROUND: The role of tractography in Gamma Ventral Capsulotomy (GVC) is unclear. Herein we describe spatial distributions of medial-orbitofrontal cortex (OFC) and lateral-OFC fibers through the anterior limb of internal capsule (ALIC), analyzing quantitative tractography parameters, differentiating OCD individuals from controls.

METHODS: Five Obsessive-compulsive disorders (OCD) patients underwent GVC (single-shot 150Gy, 4mm collimators) between 2013-2016. Five controls were randomly selected matching factors such as age, sex and DTI protocol (Diffusion-sensitizing gradient-encoding was applied in 33 directions by using a diffusion-weighted factor b=750s/mm2). Diffusion tensor image (DTI) tractography was reconstructed using Brainlab Elements (Brainlab AG, Feldkirchen, Germany). Deterministic fiber tracking (fractional anisotropy=0.15, minimum fiber-length=50 mm, maximal angulation=13) was used in all cases to reconstruct fibers from OFC.

RESULTS: Five OCD patients and five controls were included, mean age respectively, 28 ± 4.4 and 31 ± 5.8 (p=0,33). Four (80%) were men in each group. Twenty hemispheres were analyzed. Medial-OFC fibers are localized more ventral in the ALIC than lateral-OFC fibers in all hemispheres, the level of intersection and exact topography of fiber bundles are variable among individuals, especially among controls where intersection seems more prominent.  Medial- and lateral-OFC fiber tracts from right control hemispheres have lower volume than medial and lateral counterparts of OCD patients (p=0,003 and p=0,046, respectively). On the left side, only control lateral-OFC fiber bundles have lower volume than OCD patients. There are no significant differences between OCD and control concerning mean fractional anisotropy and mean fiber length.

CONCLUSIONS: Medial and lateral OFC tract fibers have a general standard distribution, lateral-OFC more dorsal than medial-OFC fibers. There are differences between OCD and control patients regarding fiber tracts volume, supporting OCD fiber tracking singularities justifying studies to identify specific targets based on DTI tractography. This needs to be validated in large clinical series.

Bruno FERNANDES DE OLIVEIRA SANTOS (Aracaju, BRAZIL), Alessandra AUGUSTA GORGULHO, Rafael COSTA LIMA MAIA, Antonio CARLOS LOPES, Crystian WILIAN CHAGAS SARAIVA, Anderson MARTINS PASSARO, Euripedes CONSTANTINO MIGUEL, Antônio AFONSO FERREIRA DE SALLES
10:55 - 11:05 #17837 - b24-2 Tractography-based targeting of the ventral capsule/ventral striatum for obsessive compulsive disorder.
b24-2 Tractography-based targeting of the ventral capsule/ventral striatum for obsessive compulsive disorder.

Objectives

Obsessive compulsive disorder (OCD) is refractory to conventional therapies in 10% of the cases, requiring procedural interventions. In a recent meta-analytic study, our group found superiority of neuroablation procedures (i.e. capsulotomy) over deep brain stimulation. Here, we (1) use ventral capsule-ventral striatum (VC/VS) probabilistic tractography to optimize targeting for neuroablation and (2) merge our tractography results to postoperative images of our gamma-knife capsulotomy patients.

Methods

Probabilistic tractography was used to analyze diffusion MRI from 40 healthy Human Connectome Project subjects to assess which portion of the VC/VS has higher streamline probability to brain regions thought to mediate obsessions, compulsions, and other motivated behaviors, namely the ventromedial prefrontal cortex (vmPFC), insula, amygdala, hippocampus, orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (dlPFC, divided in middle and superior frontal gyri) and inferior frontal gyrus (IFG). The VC/VS was used as seed, and each region of interest (ROI) as target. A tractography-based atlas of the VC/VS was derived from our results for targeting purposes. Our atlas was overlaid to the post-operative MRI images of non-responders as well as a responder treated with gamma-knife capsulotomy.

Results

Probabilistic tractography allowed identification of subregion-specific VC/VS connections. Subregions were visualized within the human VC/VS according to its streamline probability to either the vmPFC, amygdala, insula, hippocampus, OFC, dlPFC, or IFG. The dorsal-most VC region presented high streamline probability to these ROIs, except middle frontal gyrus, and this pattern was similar in the ventral VS. Notably, post-procedure imaging of responders revealed that incorporation of this dorsal-most VC subregion was required. Conversely, the ventral-most VC and dorsal VS presented lower streamline probability to these ROIs, and non-responders received a single shot targeting this ventral-most VC.

Conclusions

Probabilistic tractography allows targeting connections relevant to OCD within the VC/VS. Poorer outcomes occurred when gamma-knife failed to target dorsal VC connections. Augmenting capsulotomy with ventral VS targeting warrants further investigation. We will leverage this methodology in trials using radiosurgery and high-intensity focused ultrasound.

Daniel ALVES NEIVA BARBOSA (Stanford, USA), Alessandra A. GORGULHO, Bruno F. O. SANTOS, Rafael C. L. MAIA, Antônio C. LOPES, Eurípedes MIGUEL, Jennifer MCNAB, Sameer SHETH, Antônio A. F. DE SALLES, Casey HALPERN
11:05 - 11:15 #17834 - b24-3 Asymmetries in Bilateral Gamma Ventral Capsulotomy for Obsessive Compulsive Disorder.
b24-3 Asymmetries in Bilateral Gamma Ventral Capsulotomy for Obsessive Compulsive Disorder.

Introduction: Despite of both hemispheres being treated in the same day under identical protocol, Gamma-Knife Capsulotomy (GKC) lesions are asymmetrical in the same patient.

Objective: Evaluate lesion volume discrepancies between hemispheres after GKC for Obsessive Compulsive Disorder (OCD).

Methodology: Eight OCD-patients were treated from Dec/2014 to Oct/2017 receiving bilateral ventral-GKC (Perfexion, Elekta AB, Sweden). Treatment protocol was 150Gy delivered with a 4mm collimator. Six patients were complemented with a more dorsal GKC 14 to 27 months later. T1-MRIs were used for lesion-volume calculations (Elements®, Brainlab, Feldkirchen). Twelve-months average reduction in Yale-Brown Obsessive Compulsive Scores was 5.6 %, none achieved the expected 35% YBOCS reduction. Post–GKR MRIs were analyzed, 2 patients didn’t reach 12 months follow-up, 3 had a 2nd MRI between 7-16 months apart initial imaging. Final sample was 6 patients, 9 MRI’s and 18 lesion-volumes.

Results: Hemispheres had same treatment time, target definition and GKC parameters. The interval between first MRI and ventral-GKC was 12-21months, average 14.5months. Lesion-volumes were 0.01-0.13cm³, average: 0.045cm³. The right-side lesion was larger, average: 0.05cm³ in four cases compared to left, average: 0.03cm³. Asymmetries were 40%-500%, average: 228%. Three patients were treated first on the right side. There was no correlation between the initially treated hemisphere and lesion-volume. All lesion-volumes reduced later, range: 14.3%-100%; one disappeared. At mean 22months post-GKC lesion-volumes ranged from zero to 0.06cm³, average: 0.02cm³. The initial reported asymmetry persisted. Average volume difference was 0.023 cm³, range: 100-200%. These single isocenter lesion-volumes were insufficient to achieve the expected clinical outcomes.

Conclusion: Asymmetry was noticed in all cases during the 2-years post-GKC. Inter-hemispheric discrepancies became less prominent as the final volume established. The causes of these discrepancies are poorly understood. Larger lesions and/or in more strategic locations in the internal-capsule appear necessary for substantial decreases in YBOCS.

Rafael COSTA LIMA MAIA (São Paulo, BRAZIL), Antonio DE SALLES, Bruno FERNANDES DE OLIVEIRA SANTOS, Antônio CARLOS LOPES, Marcelo CAMARGO BATISTUZZO, Crystian WILIAN CHAGAS SARAIVA, Anderson MARTINS PASSARO, Euripedes CONSTANTINO MIGUEL, Alessandra GORGULHO
11:15 - 11:25 #17833 - b24-4 TREATMENT IMPROVEMENT FOLLOWING SINGLE-SHOT GAMMA VENTRAL CAPSULOTOMY FOR OBSESSIVE COMPULSIVE DISORDER.
b24-4 TREATMENT IMPROVEMENT FOLLOWING SINGLE-SHOT GAMMA VENTRAL CAPSULOTOMY FOR OBSESSIVE COMPULSIVE DISORDER.

Background:

Treatment refractory obsessive-compulsive disorder (OCD) is a precise indication for Gamma Knife radiosurgery, using an approach named Gamma Ventral Capsulotomy (GVC). A prior study suggested that bilateral single-shot (ss) GVC could be as efficacious as double-shot targets, but safer. In our report, we describe symptoms changes for our patients that received ssGVC. 

Methods:

Refractory OCD patients (n=5) received bilateral ssGVC (150 Gy, targeted at the ventral anterior limb of the internal capsule, with 4 mm collimator at each hemisphere). Subjects who showed to be unresponsive to ssGVC (after a minimum follow-up of 12 months) were allowed to receive additional dorsal lesions. Longitudinal assessments with psychiatric rating scales were repeated along the study.

Results:

For ssGVC, the median reductions of Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores after 12 months and 20 months of follow-up were, respectively, 13.5% and 8.1% only. There were no treatment responders. All subjects were submitted to retreatment, which consisted on adding an adjacent dorsal shot to the initial ventral one. After second shot, symptoms scores decreased by 24.1% in a median follow-up of 15 months, and two patients became partial responders. No severe or permanent side effects were described. 

Conclusion:

In this report, single-shot GVC did not show treatment efficacy in OCD. Furthermore, only the addition of adjacent dorsal shots contributed to higher rates of symptom improvement. However, treatment response remained sub-optimal in comparison to our prior cohort results, using the double shot approach. Until the last follow-up assessment of this cohort of patients, GVC showed to be safe.

Antônio CARLOS LOPES (São Paulo, BRAZIL), Stephanie KASABKOJIAN, Antônio DE SALLES, Alessandra GORGULHO, Marcelo BATISTUZZO, Marcelo HOEXTER, Marinês JOAQUIM, Maria COPETTI, Juliete MELO DINIZ, Nicole MCLAUGHLIN, Benjamin GREENBERG, Georg NORÉN, Eurípedes MIGUEL
11:25 - 11:35 #16764 - b24-5 Intracranial radiosurgery in refractory oncological and non-oncological pain.
b24-5 Intracranial radiosurgery in refractory oncological and non-oncological pain.

Introduction.

We present a series of 17 patients that have been treated with radiosurgical hypophysectomy for medically refractory oncological pain, and patients that were treated via medial radiosurgical thalamotomy for refractory trigeminal neuralgia pain, using a Rotating Gamma Ray Unit.

Radiosurgical technique.

Stereotactic frame was placed under local anesthesia, images were acquired with a 1.5 tesla MRI T1MPR 1mm slices of the zone of interest hypophysis, brainstem, optic apparatus, and thalamus region for thalamotomy. For hypophysectomy procedure a single 8mm shot was placed in the neurohypophysis and a prescription dose of 150 Gy was delivered. In the cases of medial thalamotomy a 4 mm shot was placed 4 mm anterior to PC (Y) and 4 to 6 mm lateral to the thalamic border (X) and 3 to 5 mm cephalic in Z, the prescription dose was 140 Gy.

Patient series and results.

Hypophysectomy.

11 patients have been treated thus far, follow up has been 106 days on average until the death of the patient (14-393). Positive pain response (VAS of 5 or more) was 81.8% 9/11 patients. Median VAS 3 (1-4) from the scale of 10 pretreatment. Time to response 4.8 days. No complications to report.

Medial Thalamotomy.

6 patients have been treated thus far, on average follow up has been 32 weeks (1-84), 1 patient died at 4 weeks of unrelated causes with a 70% response to his pain. Average VAS is 2.4 (1-4) for the whole series, response has been 100%. Average time to sustained response (more than 15 days) is 4.8 weeks (1-10), there are no complications to report. 3 (50%) patients recurred, one at 24 months with full installment of her pain, the two others had an 80% response in VAS at at week 20 and 16 all though pain remains in 6 in one and 10 in the other.

Conclusion.

Hypophysectomy for alleviating pain in oncological terminal patients has proven to be effective and safe. Medial thalamotomy for “central” facial pain is effective and safe although lasting effect and recurrence are yet unknown.

Eduardo LOVO (San Salvador, EL SALVADOR), Fidel CAMPOS, Victor CACEROS, William REYES , Claudia CRUZ, Juan ARIAS ROSA
11:35 - 11:45 #16940 - b24-6 Biologically effective dose (BED) is a stronger predictor compared with the dose in classical trigeminal neuralgia treated with Gamma Knife surgery.
b24-6 Biologically effective dose (BED) is a stronger predictor compared with the dose in classical trigeminal neuralgia treated with Gamma Knife surgery.

Object:To determine the impact of the biologically effective dose (BED) on the clinical outcome for cases of classical trigeminal neuralgia (CTN) treated with Gamma Knife radiosurgery (GKS), as compared with the physical prescription dose delivered over variable overall treatment times. 

Methods:Between July 1992 and November 2010, 408 CTN cases, with more than one-year follow-up, had the appropriate clinical and dosimetric (including BED) data available for analysis. The median follow-up period was 43 months (12-156.7 months). The median BED was 2243.95 Gy2.47 (mean 2232.7 Gy2.47; range 1539.4 – 2665.5 Gy2.47, showing a 75 % increase). The impact of these BED values on patient outcome were analyzed and compared with the effect of the total physical prescribed dose alone. 

Results:No significant increase in the initial pain cessation was associated with escalating BED values. However, the onset of new hypoesthesia was highly correlated with BED. For this specific outcome, BED was a strong predictor of the risk of this effect, while the physical prescribed dose was not. Maintenance of pain relief up to 2 years after GKS was again not associated with higher BED values. The data suggested that a BED value of around 1820 Gy2.47represented a good therapeutic windowsince this was associated with a ~ 5% risk of hypoesthesia, while maintaining long term pain freedom relief rate of ~90%. 

Conclusion:Dose prescription has been classically considered the best predictor for efficacy (and in some cases for toxicity). In the present analysis,physically prescribed dose showed no effect on pain relief or hypoesthesia rates. BED showed no difference for immediate or long-term pain relief, which was maintained at a high level of ~ 90%. However, the analysis revealed an increase of hypoesthesia rates for higher BED values.

Constantin TULEASCA (Lausanne, SWITZERLAND), Ian PADDICK, John HOPEWELL, William T MILLAR , Hussein HAMDI, Marc LEVIVIER, Jean RÉGIS
11:45 - 11:55 #17724 - b24-7 Gamma knife stereotactic radiosurgery for trigeminal neuralgia secondary to multiple sclerosis: a matched case-control study.
b24-7 Gamma knife stereotactic radiosurgery for trigeminal neuralgia secondary to multiple sclerosis: a matched case-control study.

Context

The efficacy of stereotactic radiosurgery (SRS) for idiopathic trigeminal neuralgia (TN) is well established, with a meta-analysis of 65 studies reporting a rate of pain-free response of 85%. The benefit of SRS for TN in the setting of multiple sclerosis (MS) remains uncertain. Such cases are often excluded from TN SRS studies and are felt to have a less favorable outcome. We performed a case-control study of patients who underwent SRS for MS-associated vs. idiopathic TN to compare pain evolution in both entities and identify risk factors for failure.

Methods

Patients treated by SRS for TN secondary to MS were retrospectively identified. The control cohort was generated using a propensity score (PS) matching algorithm. Briefly, the PS was calculated by performing a logistic regression on the complete dataset of 909 patients who underwent Gamma Knife SRS for trigeminal neuralgia at our center. The model used 11 prospectively collected variables (sex, year of treatment, age at SRS, pain level, frequency of crises, number of medications, burning sensation, electric shock sensation, loss of sensation, previous MVD and previous rhizotomy) to predict the probability of a patient having a diagnosis of MS. Then, MS patients (cases) were matched to 2 non-MS patients (controls) having a propensity score within 0.15. This yielded a final control cohort of 131 patients for 76 cases. For each patient, basic demographic data, past management, medication, subsequent treatment as well as pain characteristics at baseline and at each follow-up were collected. The primary outcome was the change in BNI pain scale distribution at last follow-up.

Results

Data collection is now complete and the results will be presented at the ISRS 2019 meeting.

Conclusion

This study will provide high level evidence on the efficacy of SRS for MS-associated TN and should improve patient selection and outcomes in this challenging population.

William LEDUC, Christian IORIO-MORIN, David MATHIEU (Sherbrooke, CANADA)
Segovia Break Out

Monday 10 June

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C24
10:45 - 12:00

Oral Session
OTHER BENIGN TUMORS

Moderators: Joao Gabriel GOMES (Neurosurgeon) (Recife, BRAZIL), Samuel RYU (Professor) (Stony Brookn NY, USA), Isaac YANG (Associate Professor) (Los Angeles, USA)
10:45 - 10:55 #17899 - C24-1 A modified disease specific graded prognostic assessment (ds-GPA) scale for melanoma consisting of age, karnofsky performance score (KPS), cumulative intracranial tumor volume (CITV), and BRAF mutation status.
C24-1 A modified disease specific graded prognostic assessment (ds-GPA) scale for melanoma consisting of age, karnofsky performance score (KPS), cumulative intracranial tumor volume (CITV), and BRAF mutation status.

ABSTRACT

Introduction:  Survival prognostication is an important aspect of personalizing oncologic care for patients with melanoma brain metastasis (BM).  We previous demonstrated the utility of a cumulative intracranial tumor volume modified diagnosis-specific graded prognostic assessment scale (CITV-dsGPA) for SRS-treated melanoma BM patients. Pertinent prognostic variables in this model included age, Karnofsky performance status (KPS), and CITV.  Here we determined whether the incorporation of BRAF mutation status into this CITV-modified scale further enhanced its prognostic accuracy.   

Methods:  We collated the survival pattern of 331 melanoma BM patients with known BRAF mutation status treated with stereotactic radiosurgery (SRS) and validated our findings in an independent cohort of 174 patients. All patients with BRAF mutation were treated with BRAF inhibitors. The prognostic utility of the model with and without BRAF mutation information was compared using the net reclassification index (NRI > 0) and integrated discrimination improvement (IDI) metric.

Results:   BRAF mutation status is an important determinant of clinical survival in both univariate analysis (Hazard Ratio for death for BRAF mutated melanomas (HR) = 0.74, p<0.001 as well as a multi-variate Cox proportional hazard model that included age, KPS, and CITV (HR for BRAF mutated melanoma = 0.72, p < 0.001).  Addition of BRAF mutation status to the CITV-ds-GPA model for melanoma significantly improved its prognostic value, with NRI > 0 of 0.294 (p=0.01) and IDI of 0.017 (p=0.02). We validated these the prognostic utility of this model in an independent cohort of 174 melanoma patients.  

Conclusions:  Optimal survival prognostication for SRS-treated patients with melanoma BM requires an integrated assessment of age, KPS, CITV, and BRAF mutation status.

Ahluwalia MANMEET, Clark CHEN (Minneapolis, USA)
10:55 - 11:05 #17750 - c24-2 Management of Trigeminal Schwannoma with Gamma Knife Radiosurgery.
c24-2 Management of Trigeminal Schwannoma with Gamma Knife Radiosurgery.

Objective:

Trigeminal Schwannomas are second most common intracranial Schwannomas. They have been traditionally treated by microsurgery which is associated with significant morbidity, and complete excision is challenging. Gamma knife radiosurgery (GKRS) is a minimally invasive alternative. This study evaluates the radiological and clinical outcome in a series of Trigeminal schwannomas’ patients treated with Gamma Knife radiosurgery.

Material and Methods:

Thirty patients were treated with Leksell Gamma Knife between May 2008 till  Dec.2018. Mean age at treatment was 43.4 yrs (Range 21-65Yrs).GKRS was used as initial treatment in 24 patients (80%) after initial subtotal resection in 4 patients(20%).The tumor volume ranged from 0.5 cc to19.3 cc (Men, 3.8cc).Mean prescription  dose was 13.2 Gy at 50 % isodose line (range. 12.5Gy to 14 Gy).

Results:

Average follow up was 48.4months ( range 6-124 months).Tumor size remained static in 16 (53.3%) and showed radiological evidence of shrinkage in 12 (40%).Tumor progression occurred in 2 (6%) patients. No patient had worsening of pre-existing neurologic symptoms or development of new cranial nerves deficits at the last follow up.

Conclusion:

GKRS is a safe and effective treatment alternative for patients with Trigeminal nerve schwannoma. There is not only long term tumor control but also functional preservation.

M Abid SALEEM (Karachi, PAKISTAN), A Sattar M HASHIM, Azhar RASHID
11:05 - 11:15 #17727 - c24-3 Stereotactic radiosurgery for oculomotor nerves schwannomas: an international multicenter study.
c24-3 Stereotactic radiosurgery for oculomotor nerves schwannomas: an international multicenter study.

Cranial nerve schwannomas are radiosensitive tumors that are commonly managed by stereotactic radiosurgery (SRS). There is a large body of literature supporting the use of SRS for vestibular and trigeminal schwannomas. Schwannomas affecting the oculomotor nerves (cranial nerves III, IV and VI) are rare tumors. They are skull base tumors in close proximity the brainstem and often involving the cavernous sinus, for which resection can cause significant morbidity. As for other schwannomas, SRS can be used to manage these tumors, but only a handful of cases have been published so far, often among other uncommon schwannoma location reports. 

The goal of this study was to collect retrospective multicenter data on tumor control, clinical evolution and morbidity after SRS. This study was performed through the International Radiosurgery Research Foundation (IRRF). To be included, patients had to be treated with single fraction SRS for an oculomotor nerve schwannoma. The diagnosis was based on either diplopia or ptosis as the main presenting symptom as well as anatomic location on the trajectory of the presumed cranial nerve of origin, or prior surgical resection confirming diagnosis.

7 institutions submitted data for a total of 25 patients. There were 11 CN III schwannomas, 11 CN IV schwannomas and 3 CN VI schwannomas. Data analysis is ongoing, and further results will be available at the meeting.

Anne-Marie LANGLOIS, Christian IORIO-MORIN, Andrew FARAMAND, Ajay NIRANJAN, L.dade LUNSFORD, Nasser MOHAMMED, Jason SHEEHAN , Roman LISCAK, Dusan URGOSIK, Douglas KONDZIOLKA, Cheng-Chia LEE, Huai-Che YANG, Atik AHMET, David MATHIEU (Sherbrooke, CANADA)
11:15 - 11:25 #17758 - c24-4 Long-Term Outcome of Gamma Knife radiosurgery for cavernous hemangioma of the orbital apex.
c24-4 Long-Term Outcome of Gamma Knife radiosurgery for cavernous hemangioma of the orbital apex.

Objective  This study was performed to analyze the long-term outcome of Gamma Knife radiosurgery (GKRS) in a series of 28 patients with cavernous hemangioma of the orbital apex. Methods  Twenty-eight patients with cavernous hemangioma of the orbital apex were treated with GKRS between March 2005 and June 2014. The series included 11 male and 17 female patients with an average age of 40.5 years (range 22–65 years). The diagnoses were confirmed by histology in 1 cases and presumed in accordance with clinical and radiological findings in 27 cases. The mean volume of the lesion at GKRS was 1.9±1.1cm3 (range 0.2~8.9cm3). The prescription peripheral dose ranged from 10.0 to 14.0 Gy. All patients had no history of radiation therapy. Results The median duration of follow-up was 52.5 months (range 24–120 months).Periodically scheduled MRI/CT and clinical follow-up showed evidence of tumor shrinkage in 26 patients (92.9%). Visual acuity (VA) was preserved in all cases. Thirteen patients (46.4%) experienced vision improvement of varying degrees, and VA was stable in 12 cases (42.9%) . Deterioration in VA was observed in only 3 cases (10.7%), including 2 patients had transient visual impairment within two weeks after GKRS. Exophthalmos disappeared on clinical ophthalmic examination in 14 cases. Only 4 cases (14.3%) had a transient chemosis. No recurrence was found during the follow-up examinations.  Conclusions This retrospective investigation indicates that GKRS provides an long-term effective management strategy in patients with cavernous hemangioma of the orbital apex, with a high rate of visual function preservation.

Dong LIU (Tianjin, CHINA), Desheng XU
11:25 - 11:35 #17721 - c24-5 Multi-fraction stereotactic radiosurgery for large cavernous sinus hemangiomas: 10 years outcomes of 88 cases.
c24-5 Multi-fraction stereotactic radiosurgery for large cavernous sinus hemangiomas: 10 years outcomes of 88 cases.

Objective: Cavernous sinus hemangiomas (CSHs) are rare vascular tumors. This study aimed to clarify the 10 year  outcomes of multi-fraction stereotactic radiosurgery  for the treatment of large CSHs(10 cm3 <tumor volume</=40 cm3).  Methods: Between January 2008 and January 2018,  Eighty-eight patients with large CSHs (10 cm3 < tumor volume</=40cm3) underwent multi-fraction Cyberknife radiosurgery . Eighty-five(96%) patients underwent multi-fraction stereotactic radiosurgery as the primary management for their CSHs based on clinical and imaging criteria, and the other three patients had previous operation before multi-fraction stereotactic radiosurgery. The median volume of the CSHs was 23.9  cm3 (range, 10.3-40.0 cm3). Multi-fraction stereotactic radiosurgery was delivered in 3 fractions. The median marginal dose was 20.3 Gy (range, 19.5–21 Gy) prescribed to a median 64% isodose line. Results:  The median follow-up period was 56 months (range, 12–123 months). Tumor control was achieved in all patients (100%) during the follow-up period. At 12 months after cyberknife radiosurgery, MRI revealed a mean of 80% tumor volume reduction (range, 60%-99%). The last MRI showed a mean of 90% tumor volume reduction. Sixty-six( 75%)patients who had cranial neuropathies before radiosurgery demonstrated improvements in their neurological deficits (improvement of vision, facial numbness), 16(18%) patients initially asymptomatic kept the same clinical status, 4 patients developed mild facial numbness.  One patient reported a stroke 3 years post radiosurgery because of hypertension. One elder patient felt reduction of memory post radiosurgery. No patient had visual function deterioration, and other adverse radiation effects during the follow-up period. Conclusion: Our experience confirms that multi-fraction stereotactic radiosurgery is a safe and an effective management strategy for large CSHs. Considering the risk involved in microsurgery, multi-fraction SRS may serve as the primary treatment option for patients with large CSHs.

Enmin WANG, Enmin WANG (Shanghai, CHINA), Xin WANG, Li PAN, Huaguang ZHU, Xiaoxia LIU, Yang WANG
11:35 - 11:45 #17771 - c24-6 Cyberknife radiosurgery for jugular foramen schwannomas: long-term outcomes.
c24-6 Cyberknife radiosurgery for jugular foramen schwannomas: long-term outcomes.

OBJECTIVE  Jugular foramen schwannomas (JFSs) are rare lesions and controversy regarding their management still exists. Complete resection is possible but may be associated with significant morbidity. Stereotactic radiosurgery (SRS) is a minimally invasive alternative or adjunct to microsurgery. The authors reviewed clinical and imaging outcomes of Cyberknife SRS for patients with these tumors.

METHODS   Fifty-nine patients with JFSs underwent hypofractionated Cyberknife radiosurgery between January 2008 and January 2015. Thirteen patients had previous microsurgical resection, one patient had recurrent tumor post Gamma Knife radiosurgery, the rest 45 patients underwent Cyberknife radiosurgery based on their neuroimaging and clinical manifestations. Fifty-four patients had preexisting cranial nerve (CN) symptoms and signs. The median tumor volume was 15.1 cm3 (range 2.6-36.0 cm3), and 39 of them was larger than 10cm3 in volume. The radiation dose prescribed to the tumor margin and the number of fractions depend on the tumor volume. Twelve patients with large tumors were treated in 4 fractions, 31 patients were treated in three fractions and 16 patients in two fractions. The median margin dose was 19.2 Gy/2 Fx ( fractions),  21.1Gy/3Fx  and 24.5Gy/4Fx. Patients with neurofibromatosis were excluded from this study.

RESULTS  The median follow-up was 58 months (range 24-105 months). Tumors regressed in 41(69%) patients, remained stable in 14 and progressed in 4. The progression-free survival (PFS) was 93% at 5 years, Preexisting cranial neuropathies improved in 32 patients, remained stable in 10 patients, and worsened in 17 patients.  Four patients underwent resection at a median of 14 months after Cyberknife SRS (range 8-30 months).

CONCLUSIONS  Cyberknife radiosurgery proved to be a safe and effective primary or adjuvant management approach for JFSs. Long-term tumor control rates and stability or improvement in CN function were confirmed.

Enmin WANG, Enmin WANG (Shanghai, CHINA), Xin WANG, Huaguang ZHU, Xiaoxia LIU, Yang WANG, Li PAN
11:45 - 11:55 #17860 - b28-6 Postoperative Stereotactic Radiosurgery for Spinal Metastases: Clinical Outcomes, Failures, and Analysis of Local Control.
Postoperative Stereotactic Radiosurgery for Spinal Metastases: Clinical Outcomes, Failures, and Analysis of Local Control.

Stereotactic radiosurgery (SRS) is a viable treatment modality for spine metastases. SRS is increasingly being used in the multimodal management of these patients. Results of post-operative stereotactic radiosurgery following separation surgery has been reported but clinical outcomes and local control for a more heterogenous surgical sample (i.e., anterior approaches, anterior column reconstruction, revision surgery after previous SRS) is lacking in the literature. We present data on clinical outcomes and local tumor control at a major cancer center following contemporary surgical approaches for spine metastases.

After IRB approval, retrospective review of patients between 2012 and 2017. Demographic information, tumor histology, survival rates, recurrence rates, clinical outcomes and complications were recorded and analyzed

 

The mean age of patients in our cohort was 64 years (range 44 to 85 years), with 32% female.The radiation dose was 18 Gy in 1 fraction using 6 MV photons with a 24Gy boost to the gross tumor volume.The follow up period range was 3-84 months, with average time between surgery (11.1% anterior approach, 88.9% posterior approach) and SRS 3 weeks. Radiographic evaluation following SRS was every 3 months after treatment with CT or MRI. The 1- and 2-year survival rates were 57% and 38% respectively. The overall rate of local recurrence was 12.7% within the follow up period. Multivariate analysis revealed tumor location (thoracic) and histology (lung carcinoma, colon adenocarcinoma, or melanoma) as significant prognostic factors for local control and overall survival. The overall surgical and medical complication rates were 14.3% and 19.0% respectively.  The most common complication after SRS was an acute pain flare. The rate of hardware failure was 6.3%, with 3 patients developing procedure-related neurological deficits, but there were no cases of radiation myelopathy. Eighteen patients required additional surgery for metastatic disease at adjacent or distant spinal levels. There were no differences in local control if a patient had anterior column reconstruction or not.

 

SRS is an effective treatment modality following all types of surgery for metastases, not just separation surgery. SRS should be considered in the post-operative management for spinal metastases given the low complications, and local control roughly 87% irrespective of histology.

John SHIN (Boston, USA), Muhamed HADZIPASIC, Laura VAN BEAVER, Caroline AYINON, Robert KOFFIE, Brian WINEY, Thomas BOTTICELLO, Ganesh SHANKAR, Joseph SCHWAB, Kevin OH
El Pardo I
12:00

Monday 10 June

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B25
12:00 - 13:00

Oral Session
GENITOURINARY

Moderators: Patrick KUPELIAN (Professor) (Palo Alto, USA), Ernesto ROESLER (Head of the Department) (Recife, BRAZIL), Deivid Augusto SILVA (BRAZIL)
12:00 - 12:10 #17634 - b25-1 CyberKnife based radioablation of 500 LR and IR prostate cancer patients - single center results.
b25-1 CyberKnife based radioablation of 500 LR and IR prostate cancer patients - single center results.

Objectives: An evaluation of effectiveness and toxicity of LR and IR prostate cancer patients (PCP) CyberKnife (CK) based radioablation.

Methods: Consecutive 500 PCP (LR 264  and IR 236) were irradiated with fd 7.25 Gy to TD 36.25 Gy. Median FU was 31.3 months. PSA, ADT uptake and toxicity using EORTC/RTOG scoring system were checked (acute effects to 4 months, next, late ones). ROC curves were created and appropriate AUC were calculated for different PSA values as predictors of failures. Two-way analysis of variances was used for PSA course evaluation.

Results: During FU 15 failures appeared (6 biochemical failures, 2 local relapses, 5 locoregional-pelvic  nodal disseminations and 2 bone metastasis). Median time to failure was 19.9 months (22.5 to relapse and 17.5 to dissemination). Percentage of patients without ADT increased from 44.6% before RT to 100% 56 months later. In this period PSA median decreased from 2.8 to 0.12. Percentage of patients without gastrointestinal (GI) toxicity varied from 90.2% at the RT end to 100% 56 months later. There was one G4 toxicity: rectourethral fistula revealed 26 months after RT. Percentage of patients without genitourinary (GU) toxicity was smaller and varied from 74.5% 1 month after RT to 97.9% 44 months after RT. No G4 GU toxicity was noted.  Higher PSA values during FU (even not filled Phoenix criterion), before failure appearance were connected to high risk of failure later on. PSA concentration during FU was significantly higher for IR patients without ADT.

Conclusions: CK based radioablation of LR and IR PCP is safe, effective treatment. Higher PSA during first part of FU is strong predictive factor for a treatment failure. Lack of ADT in the group of IR patients results in higher PSA, so ADT administration for these patients may benefit with lower PSA and, finally with better treatment results.

Leszek MISZCZYK (Gliwice, POLAND), Aleksandra NAPIERALSKA , Malgorzata KRASZKIEWICZ, Agnieszka NAMYSL-KALETKA, Grzegorz WOZNIAK, Malgorzata STAPOR-FUDZINSKA MALGORZATA, Marcin MISZCZYK, Andrzej TUKIENDORF
12:10 - 12:20 #17666 - b25-2 CyberKnife robotic radiosurgery for intermediate unfavorable and high-risk prostate cancer patients: initial results.
b25-2 CyberKnife robotic radiosurgery for intermediate unfavorable and high-risk prostate cancer patients: initial results.

Introduction: The role of radiosurgery for intermediate unfavorable-risk (IUFR) and high-risk (HR) prostate cancer (pCa) patients is not clear. Patients which refuse other treatment methods might benefit from local application of radiosurgery if involvement of pelvic lymph nodes is excluded.

Materials and methods: From June y.2016 to January 2019 12 IUFR and 11 HR prostate cancer patients were treated with local application of robotic radiosurgery with CyberKnife M6 system to prostate and seminal vesicles. All patients whose risk of pelvic lymph node involvement were above 7% according to MSKCC risk calculator were advised to undergo  PSMA PET-CT. 4 fiducial markers were implanted according Accuray recommendations. CT and MRI topometry was done with following delineation of prostate and 1-2cm proximal seminal vesicles (CTV). Safety margin of 5mm in all directions except 3mm posteriorly were added for PTV. Dose of 35-36.25 Gy were prescribed to PTV with focal increase of the dose to dominant lesion (GTV) visible on MRI and PET-CT. Median pretreatment PSA was 7.98 ng/ml [range 0.21, 60]. PSA level was evaluated before treatment and every 3 months after treatment. 6 patients received ADT before treatment or short term (3-6 months) after SRS. Follow-up ranged from 3 months to 30 months (median 11.5 months). Minimal dose to GTV was applied 36.22 Gy, maximal 53.62Gy (median 42.32 Gy). Early toxicity was evaluated according RTOG/EORTC toxicity scale.

Results:  PSA values decreased for all patients reaching values of 0.1 - 4.58 (median 1.385) ng/ml. There were no biochemical relapse detected according Phoenix criteria (nadir+2) however 1 high-risk patient had PSA increase from 0.231 ng/ml (nadir) to 1.4 ng/ml during follow-up of 9 months. For one high-risk patient ADT was prescribed after minor PSA increase - from 0.13 ng/ml (nadir) to 0.259 ng/ml in 6 months. All patients (96%) had Grade 0-2 toxicity, except one (4%) who had grade 3 rectal toxicity due to inflammation in rectal wall.

Conclusions: Initial data suggests that FSRS provides significant PSA decrease for all IUFR and HR prostate cancer patients. Focal increase of radiation dose does not increase Grade 3 toxicity comparing to published data. Longer follow-up and larger number of patients in multi-institutional data registries might help clarify the role of FSRS for these groups of patients.

Maris MEZECKIS (Sigulda, LATVIA), Kirils IVANOVS, Egils VJATERS, Sandra CIPKINA, Vladislav BURYK
12:20 - 12:30 #17689 - b25-3 Pattern of progression after stereotactic body radiotherapy of oligorecurrent prostate cancer patients.
b25-3 Pattern of progression after stereotactic body radiotherapy of oligorecurrent prostate cancer patients.

Purpose

To determine the pattern of progression after stereotactic body radiotherapy (SBRT) of oligorecurrent prostate cancer patients.

Material and Methods

Study group consisted of 86 patients(pts) with 120 metastatic lesions – 77 in lymph nodes (LN) and 43 in bones (BM) treated with SBRT (mean total dose of 36 Gy in 3 fractions). Primary treatment was surgery (16pts), surgery+ RT (28pts, in 9 with elective nodal irradiation–ENI), prostate only RT (24pts), prostate RT+ENI (18pts). PET-CT was used in diagnosis in 84% of pts. Oligorecurrence was diagnosed in 29 pts (34%) during hormonal treatment (HT), remaining 66% were not on HT at that time. Oligorecurrence in LN was regional (defined as LN below L5) in 28 pts (48 LN) and distant in 23 pts (29 LN). Among 59 patients without ENI, oligorecurrence in regional LN occurred in 19 pts, as compared to 5 pts with ENI. 

Results

Median follow-up was 3 years after SBRT. One-, 2- and 3-year overall survival (OS) was 95%, 87% and 78%, respectively. Progression after SBRT was observed in 45 pts (still oligometastatic in 26 pts, disseminated in 19 pts) and 1-, 2- and 3-year progression-free survival (PFS) was 67%, 45% and 36%, respectively. Majority of  pts with LN oligorecurrence who had clinical progression after SBRT developed LN metastases (83%), while majority of  pts with BM oligorecurrence developed BM (89%). Among 28 pts diagnosed with oligorecurrence in regional LN there were 13 pts with nodal recurrence after SBRT: regional LN in 5, regional and distant in 6 and distant LN in 2 pts. Almost all pts with oligorecurrence in distant LN had progression in distant LN (majority in common iliac above L5 – 11 pts or retroperitoneal/paraaortic LN – 9 pts). Progression after SBRT in pts without previous ENI was within regional LN in 61% in contrast to only 1 pts given previous ENI with progression in regional LN after SBRT. Patients with oligorecurrence diagnosed during HT compared to those who were not on HT while diagnosed with oligorecurrence had worse PFS (p=0.0008) and worse overall survival (p=0.001).

Conclusions

Pattern of progression after SBRT in oligorecurrent prostate cancer pts is strongly associated with previous metastasis location. Patients with previous ENI tend to progress outside regional lymph nodes. Progression during HT predicts worse outcome despite of applied further treatment.

Aleksandra NAPIERALSKA (Gliwice, POLAND), Wojciech MAJEWSKI, Małgorzata STĄPÓR-FUDZIŃSKA, Leszek MISZCZYK
12:30 - 12:40 #17765 - b25-4 Evaluation of outcomes after stereotactic hypofractionated radiotherapy for prostate cancer.
b25-4 Evaluation of outcomes after stereotactic hypofractionated radiotherapy for prostate cancer.

Aims: Several randomized trials support the use of high doses of radiation for localized prostate cancer. We retrospectively report collected data from a cohort of localized prostate cancer patients treated with Cyberknife (CK) in our Center.
Methods: From July 2007 through June 2016 a retrospective analysis was carried out on 217 pts with a median age of 75 years (range 52 – 86), median prostate volume of 75.6 cc (range 37.03-163.16)and clinically localized prostate cancer. CK was used to deliver fiducials based image guided Stereotactic Body Radiotherapy Treatment . The majority of pts 116 (53%) were low risk , 60 pts (28%) were intermediate risk and 41 patients (19%) were high risk (according to the NCCN criteria). Median pre-treatment PSA was 8.51 ng/ml (range 1.51- 51 ng/ml) .17 (41%) of 41 high risk pts received Androgen Deprivation Therapy. The course of radiotherapy consisted of 38 Gy over 4 fractions (9.5 Gy per fraction) given daily to the PTV. Heterogenous dose planning was used, dose was normalized to the 75% isodose line in order for the prescription dose to cover at least 95% of PTV. Real-time intrafractional motion tracking was used.
Results: With a median follow up of 61 months (range 12 – 120), the six years actuarial PSA relapse free survival rate is 94.4% (CI: 90.8%-98.2%) with 98.2% for low risk, 94.5% for intermediate and 85.6% for high risk. 23 (10.5%) pts died during the follow up for unrelated causes, only one (0.5%) died for prostate cancer. Limited acute urinary symptoms(grade I - II) were common (46.5% of pts), no one experienced grade III or worse acute urinary symptoms. 20.3% of pts reported grade I or II acute GI symptoms, only one experienced a grade III acute proctitis. No grade IV rectal toxicity was observed. The majority of pts (78.3%) experienced grade 0 GU late toxicity, 39 (18 %) experienced grade I or II GU symptoms, 7 (3%) pts reported grade III toxicity. In one patient (0.5%) a grade IV bladder fistula was observed. The majority of pts (95%) did not experienced late GI toxicity, only Grade I or II symptoms were observed in 10 patients (4.6%),higher was not reported.
Conclusions: Cyberknife SBRT represents a non invasive method for the definitive treatment of localized prostate cancer with results not inferior to standard fractionated radiotherapy in terms of biochemical control rates at up to 6 years and toxicities.

Giancarlo BELTRAMO, Giovanni LONGO, Isa BOSSI ZANETTI (Milano, ITALY), Achille BERGANTIN, Anna Stefania MARTINOTTI, Irene REDAELLI, Paolo BONFANTI, Chiara SPADAVECCHIA, Livia Corinna BIANCHI, Matteo MAGGIONI, Guido DORMIA
12:40 - 12:50 #17787 - b25-5 Phase 2 multicentre study of gantry-based SBRT boost for intermediate and high risk prostate cancer.
b25-5 Phase 2 multicentre study of gantry-based SBRT boost for intermediate and high risk prostate cancer.

Objectives: To report feasibility, early toxicity and PSA kinetics following gantry linac-based, stereotactic radiotherapy (SBRT) boost within a prospective, phase 2, multicentre study (PROMETHEUS: ACTRN12615000223538)

Methods: Patients were treated with gantry-based SBRT, 19-20Gy in 2 fractions delivered one week apart, followed by conventional IMRT (46Gy in 23 fractions). The study mandated MRI fusion for planning, rectal displacement and intrafraction image guidance. Toxicity was prospectively graded using CTCAE v4.  

Results: Between March 2014 and July 2018, 135 patients (76% intermediate, 24% high-risk), median age 70 years (range 53–81) were treated across five centres. Short course (≤6 months) androgen deprivation therapy (ADT) was used in 36%, long course in 18%. Rectal displacement method was SpaceOAR in 59% and Rectafix in 41%. Median follow-up was 24 months.Acute grade 2 gastrointestinal (GI) and urinary toxicity occurred in 4.4% and 26.6% with no acute grade 3 toxicity. At 6, 12, 18, 24 and 36 months post-treatment the prevalence of late grade ≥2 GI toxicity was 1.6%, 3.7%, 2.2%, 0% and 0% respectively and the prevalence of late grade ≥2 urinary toxicity was 0.8%, 11%, 12%, 7.1% and 6.3% respectively. Three patients experienced grade 3 late toxicity at 12 to 18 months which subsequently resolved to grade 2 or less. For patients not receiving ADT, median PSA pre-treatment was 7.6ug/L (1.1 – 20) and at 12, 24 and 36 months post-treatment was 0.86, 0.36 and 0.20ug/L. 

Conclusions: Delivery of a gantry-based SBRT boost is feasible in a multicentre setting, is well tolerated with low rates of early toxicity and is associated with promising PSA responses. A second transient peak in urinary toxicity was observed at 18 months which subsequently resolved. Follow-up is ongoing to document late toxicity, long-term patient reported outcomes and tumour control with this approach.

David PRYOR (Brisbane, AUSTRALIA), Mark SIDHOM, Sankar ARUMUGAM , Joseph BUCCI, Sarah GALLAGHER , Joanne SMART, Greer PETER, Sarah KEATS, Lee WILTON , Jarad MARTIN
Segovia Break Out

Monday 10 June

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A25
12:00 - 13:00

Oral Session
METASTASES #1

Moderators: Eduardo LOVO IGLESIAS (Brain and Spine Radiosurgery Program) (San Salvador, EL SALVADOR), Edilmar MOURA (DIRECTOR) (NATAL, BRAZIL), John SUH (Radiation Oncologist) (Cleveland, USA)
12:00 - 12:10 #17640 - a25-1 United States radiotherapy practice patterns for brain metastases in the era of stereotactic radiosurgery.
United States radiotherapy practice patterns for brain metastases in the era of stereotactic radiosurgery.

Background: Stereotactic radiosurgery (SRS) effectively treats brain metastases (BM) while minimizing treatment-related morbidity, prompting reassessment of whole brain radiotherapy (WBRT) indications. A patterns of care analysis between SRS and WBRT was performed.

Materials/Methods: Adults in the National Cancer Database (NCDB) with BM at diagnosis from a lung, breast, skin, urogenital, gastrointestinal, or head/neck primary tumor between 2010-2015 and no prior malignancy were identified. WBRT was defined as 20-50Gy in 4-44 fractions (fx) at 1.6-6Gy/fx totaling 60-100Gy2 biologically equivalent dose delivered in ≤60 days using non-SRS external beam modality. SRS was defined as radiosurgery modality, 12-24Gy/1fx, 18-30Gy/2fx, 21-36Gy/3fx, 21-36Gy/4fx, or 25-40Gy/5fx to the brain. Radioresistant histology was defined as melanoma, renal cell carcinoma (RCC), sarcoma/spindle cell, or gastrointestinal (GI) primary. Odds ratios (OR, 95% confidence interval) of SRS receipt compared to WBRT were calculated from multivariate logistic regression. OS was estimated via the Kaplan-Meier method. The substantial limitations in using the NCDB for these analyses were critically reviewed.

Results: 90,388 subjects were identified, the majority with BM from primary lung cancer (83.0%). Of these, 11,486 (12.7%) received SRS and 24,262 (26.8%) WBRT. Annual use of WBRT decreased from 27.8% to 23.5%, while use of SRS increased from 8.7% to 17.9% in 2010 and 2015, respectively. The most common SRS and WBRT dose-fractionations were 20Gy/1fx (13.0%) and 30Gy/10fx (56.8%), respectively. Factors significantly associated with SRS receipt on multivariate analysis were later year of diagnosis (2015 vs 2010, OR 2.4, 2.2-2.6), radioresistant histology (OR 2.0, 1.9-2.2), academic facility (OR 1.9, 1.8-2.0), highest income quartile (OR 1.6, 1.4-1.7), chemotherapy receipt (OR 1.4, 1.4-1.5), and further travel distance (>15 vs ≤15 miles, OR 1.4, 1.3-1.5). Median OS was 11.7mo for SRS (OS 72% @6mo, 19% @36mo) and 5.7mo for WBRT (OS 49% @6mo, 6% @36mo).

Conclusions: WBRT utilization appears to be decreasing while SRS utilization is increasing in the U.S. to treat BM at diagnosis. BM from melanoma, RCC, sarcoma, or GI primaries are more likely to receive SRS. The data in the NCDB are inadequate to infer the efficacy of SRS over WBRT, particularly in the absence of performance status and number of BM.

Andrew BARBOUR (Durham, USA), Corbin JACOBS, Gita SUNEJA, Scott FLOYD, Jordan TOROK, John KIRKPATRICK
12:10 - 12:20 #17703 - a25-2 Stereotactic radiosurgery (SRS) for brain metastases – time trend and variation in practice in Australia.
Stereotactic radiosurgery (SRS) for brain metastases – time trend and variation in practice in Australia.

Introduction: To evaluate the trend in utilisation of stereotactic radiosurgery (SRS) for management of brain metastases (BM) in Australia

Methods: The Victorian Radiotherapy Minimum Data Set (VRMDS) captures vital details of radiotherapy (RT) delivered in the state of Victoria, Australia. This study comprise all patients in VRMDS with solid tumour (excluding primary brain malignancies) who underwent brain RT between January 2012 and December 2017. The primary outcome was any documented use of SRS. Differences in patient-, tumour-, sociodemographic and institutional factors between patients who had SRS vs. no SRS were compared using Pearson’s chi-squared test for categorical variables. The Cochrane-Armitage test for trend was used to evaluate the use of SRS over time. Multivariable logistic regression was used to identify factors associated with SRS use.

Results: Of the 3,964 patients who had brain RT included in this study, 1,348 (34%) were documented to have SRS. There was an increase in uptake of SRS from 31% in 2012 to 41% in 2017 among patients who had RT for BM (P<0.001). Patients who had SRS were younger – mean age was 63.2 (SD=12.8) in those who had SRS vs. 65.5 (SD=12.3) in those who did not have SRS (P<0.001). There were no differences in SRS use between men (34%) and women (34%) (P=0.8). Patients who had melanoma were significantly more likely to have SRS  (50%), compared to other tumour types e.g. lung cancer (26%), breast cancer (33%), or gastrointestinal cancers (31%) (P<0.001). Patients from the most disadvantaged residential areas were less likely to have SRS (29%) compared to those from least disadvantaged residential areas (45%) (P<0.001). Patients treated in public institutions were more likely to have SRS compared to private institutions (36% vs. 30%, P=0.001). Patients treated in metropolitan centres were also more likely to have SRS compared to those treated in regional centres (41% vs. 8%, P<0.001). In multivariate analysis, patients’ age, tumour type, sociodemographic factors, treatment centres, and year of RT were all independently associated with SRS use.

Conclusion: This is the largest Australian population-based cohort of patients who had RT for BM, with increasing use of SRS observed over time. There is marked variation in SRS use, depending on tumour type as well as sociodemographic and institutional factors.

Wee Loon ONG (Melbourne, Australia, AUSTRALIA), Therese KANG, Gishan RATNAYAKE, Morikatsu WADA, Jeremy RUBEN, Sashendra SENTHI, Jeremy MILLAR, Farshad FOROUDI
12:20 - 12:30 #17560 - a25-3 Safety and efficacy of dose escalation for neoadjuvant stereotactic radiosurgery for large brain metastases: results from a prospective trial.
a25-3 Safety and efficacy of dose escalation for neoadjuvant stereotactic radiosurgery for large brain metastases: results from a prospective trial.

Background: Single session stereotacic radiosurgery (SRS) alone for brain metastases larger than 2cm in maximal dimension results in local control of only 50%. Surgical resection followed by SRS to the resection cavity can result in leptomeningeal failure (LMD).

Objectives: To determine the safety, feasibility, and efficacy of neoadjuvant SRS at escalating doses followed by surgical resection of brain metastases greater than 2 cm in maximal dimension.

Methods: Patients underwent Gamma Knife SRS followed by surgical resection of brain metastases within 2 week as part of an IRB-approved trial. SRS dose was escalated based on maximal lesion dimension at 3 Gy increments from currently accepted RTOG dosing; and cohorts of 2-6 patients were treated at each dose. Initially, 2 patients were treated at a particular dose and followed for 4 months. If no dose-limiting toxicities (DLT) were observed, the dose was escalated and a new cohort of 4 patients were treated.

Results: A total of 27 patients enrolled on the trial. For tumor size >2.0 - 3.0 cm, 2 patients completed treatment at 18 Gy and 3 patients at 21Gy. For tumor size >3.0 - 4.0 cm, 4 patients were treated at 15 Gy and 9 patients were treated at 18 Gy and 1 patient at 21 Gy. For tumor size > 4.0 - 5.0 cm, 1 patient was treated at 12 Gy and 7 patients at 15 Gy.  Thirteen patients have died at time of analysis. Two patients have experienced local failure. After a median and mean follow up of 9.2 and 15.2 months, respectively, the 6 and 12 month local control was 94.7% and 94.7%, respectively. Six and 12 month distant brain control was 71.7% and 49.6% respectively. Overall survival at 6 and 12 months was 81.5% and 54.9%, respectively. One patient developed localized LMD 5 months following SRS. Twenty-six patients were evaluable for acute toxicity. No DLT have occurred. Twenty-two patients (85%) had no adverse events related to protocol treatment.

Conclusions: Neoadjuvant SRS with dose escalation followed by surgical resection for brain metastases greater than 2 cm in size results in excellent local control, acceptable acute toxicity, and very low rate of LMD failure. The maximum safe dose has not yet been reached. 

Erin MURPHY (Cleveland, USA), Kailin YANG, John SUH, Jennifer YU, Cathy SCHILERO, Alireza MOHAMMADI, Glen STEVENS, Lilyana ANGELOV, Michael VOGELBAUM, Gene BARNETT, Gennady NEYMAN, Sam CHAO
12:30 - 12:40 #17735 - a25-4 A natural history of melanoma brain metastases on MRI: Recommendations for interval from imaging to treatment delivery.
A natural history of melanoma brain metastases on MRI: Recommendations for interval from imaging to treatment delivery.

Background:

Stereotactic radiation surgery (SRS) is increasingly being used to treat brain metastases to minimize the neurocognitive side effects associated with whole-brain radiation therapy and provide good intracranial disease control. Previous studies have shown that time between pretreatment magnetic resonance imaging (MRI) and SRS is associated with intracranial progression and reduced local control. However, there are no formal recommendations regarding the timing between pretreatment MRI and SRS delivery based on a natural radiographic history of individual brain metastases.

Methods:

Retrospective review of all patients diagnosed with melanoma brain metastases between 2003 and 2018. All MRI scans, including those from outside institutions, were reviewed for radiographic change. Individual brain metastases were tracked for growth before treatment. Number of new metastases was recorded between scans. Kaplan-Meier analysis was used to evaluate frequency of radiographic change.

 

Results:

A total of 561 MRI scans were reviewed and revealed 384 brain metastases in 65 patients with metastatic melanoma. Each patient had 8.6 MRI scans and 5.9 metastases on average. Ninety metastases (23.4%) grew before treatment, 223 (58.3%) were treated before displaying any growth, and 70 (18.2%) showed no growth during observation. The median time interval between MRI scans, diagnosis and metastatic growth, and diagnosis and treatment was 73 days (IQR 28-99), 33 days (IQR 27-71), and 19 days (IQR 0-38), respectively. Seventy-two (14.8%) MRI scans displayed growth relative to the previous MRI, with a median interval of 33 days, while 98 (20.1%) MRI scans showed new metastases relative to the previous MRI, with a median interval of 70 days.

 

Conclusion:

Roughly a quarter of the observed metastases showed growth before treatment with most of the observed growth occurring between 1 and 3 months after diagnosis. This suggests that SRS delivery within 1 month of diagnosis would minimize risk of metastatic growth.

Alon KASHANIAN (Los Angeles, USA), Collin PRICE, Rebecca LEVIN-EPSTEIN, Tania KAPREALIAN, Nader POURATIAN
12:40 - 12:50 #17777 - a25-5 Stereotactic radiosurgery for small cell lung cancer brain metastases.
Stereotactic radiosurgery for small cell lung cancer brain metastases.

Purpose:

Brain metastases from small cell lung cancer (SCLC), either when newly diagnosed or recurrent following prior prophylactic cranial irradiation (PCI) or whole brain radiotherapy (WBRT), are traditionally thought to be widely disseminated and unsuited for focal stereotactic radiosurgery (SRS). For newly diagnosed metastases, we hypothesized that the rate of new distant failure (DF) elsewhere in the brain and neurologic death rate following SRS for SCLC is similar to historical controls for non-SCLC brain metastases and that SRS is suitable for salvage following prior PCI/WBRT.  

Materials & Methods:

In this IRB-approved retrospective study, we identified 59 patients with 236 total metastases treated from 2000-2017 with SRS in 90 total courses for SCLC brain metastases. Twenty-one patients had inadequate follow-up, yielding 38 evaluable patients with 153 metastases. SRS was indicated for salvage after prior PCI (12 patients (32%)) or WBRT (15 patients (32%)) or for upfront initial treatment in 11 (29%) patients. The cumulative incidences, with death and salvage WBRT as competing risks, were estimated for local (LF), distant (DF) failure, and adverse radiation effect (ARE) as were the Kaplan-Meier estimates of overall (OS) from the time of SRS.

Results:

With a median follow up of 6.2 months (range 0.1 - 91.3 months), the 1-year cumulative incidence of LF was 21% [95%CI 15%, 27%]. The rate of LF was 4% for upfront SRS compared to 27% for salvage SRS after PCI/WBRT (p=0.01). The 1-year cumulative incidence of DF was 49% [95%CI 31%, 64%]. There was no difference in DF for patient treated with upfront SRS (57% [95% CI 21%, 85%]) and salvage SRS (44% [95%CI 25%, 63%]) (p=0.36). In patients treated with upfront SRS, 46% ultimately received salvage WBRT following SRS compared to 13% with prior PCI or WBRT (13%) (p=0.08).  The 1-year rates of ARE per patient were 17% for upfront SRS and 20% for salvage SRS (p=1.00). The median OS was 5.9 months, with a crude incidence of neurologic death of 14%.

Conclusion:

Patients with SCLC treated with SRS appear to have similar rates of local failure, distant failure and neurologic death compared to historical controls of SRS for non-SCLC.    In the era of controversy regarding PCI for SCLC as well as the deferral of WBRT for NSCLC given concerns of neurotoxicity, the role of upfront SRS alone for SCLC should be re-evaluated.

Scott SOLTYS (Stanford, CA, USA), Rohil TAGGARSI, Everett MODING, Ziad FAWAZ, Rie VON EYBEN, Erqi POLLOM, Steven CHANG, Iris GIBBS, Steven HANCOCK, Hilary BAGSHAW
12:50 - 13:00 #16763 - a25-6 Symptomatic brain metastases larger than 8.5cc managed with upfront radiosurgery.
a25-6 Symptomatic brain metastases larger than 8.5cc managed with upfront radiosurgery.

Introduction.

Current recommendations in accordance with NCCN guidelines regarding management of metastases larger than 2.5 cm in symptomatic patients suggest surgery as a first choice. We analyze the role of upfront radiosurgery in such patients.

Methods.

37 symptomatic patients that harbored metastatic tumors mainly from breast histology that were greater than 8.5 cc in volume were treated from 2011 to January 2018.

Results.

The median tumor volume was 12.5 cc (8.5-78.4), 9 (24%) patients were treated with LINAC with a volume of 20 cc (9.2-70 cc). The treatments with Gamma Ray were administrated to the remaining 28 (76%) patients, 9 (32%) of them with adaptive (Staged) radiosurgery protocol. The prescription dose for the gamma group was 13.8 Gy (7.5-18Gy) mean dose of 17.9 Gy (13.2-23.3 Gy) with a mean volume of 16.3 cc (8.5-78.4 cc) for single dose and 14.5 Gy (10-18) for the first treatment of adaptive SRS to a volume of 12.8 cc (8.5-78.4) and 13.5 Gy (10-18) for the second treatment 30 days after to a 4.3cc (0.4-70) volume.

Karnofsky score was 60 (50-70) the day of treatment and 80 (60-100) at 30 days (P=0.0001). At 30 days 95% of the tumors available for scanning (20 out of 21 tumors) had reduced in size in a 74% (11-95%). Median survival was 19 months (4-34), with an accumulative risk of death from central nervous progression of 4.5%. We had reports of disease progression in 7 (18.9%) patients (RECIST), Two of them were adequately managed by steroids (Radiation necrosis). Four patients meet criteria for surgery at 7 months (4-34), 3 were operated. Of the whole series 6 (16.2%) Patients required new treatments with radiosurgery for new lesions, 3 for progression.

Conclusion.

Radiosurgery in our experience has shown to be effective in controlling large metastases in the brain, it requires a careful monitoring and neurosurgical collaboration to provide patient safety.

Eduardo LOVO (San Salvador, EL SALVADOR), Victor CACEROS, Mario MINERVINI, William REYES , Fidel CAMPOS
Segovia Plenary

Monday 10 June

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C25
12:00 - 13:10

Oral Session
PHYSICS #1

Moderators: Francine Xavier DOS SANTOS (Medical Physicist) (