Monday 20 June
Time SILVER ROOM RED 2 ROOM BLUE 2 ROOM
08:00
08:00-09:00
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A10
BREAKFAST SEMINAR
Vestibular Schwannomas

BREAKFAST SEMINAR
Vestibular Schwannomas

Moderators: Antonio DE SALLES (Professor - Chief) (SÃO PAULO, Brazil), Alberto FRANZIN (Head) (Brescia, Italy)
Coordinator: Jean REGIS (MARSEILLE, France)
08:00 - 08:20 Point – Counter point : Early versus late radiosurgery for small vestibular schwannomas with good hearing. Douglas KONDZIOLKA (New York, USA)
for “early”
08:20 - 08:40 Point – Counter point : Early versus late radiosurgery for small vestibular schwannomas with good hearing. George BOVIS (Neurosurgeon) (Chicago, USA)
for “late”
08:40 - 09:00 Biological and radiological predictors of growth in vestibular schwannomas before and after SRS. Patrick LANGENHUIZEN (Researcher) (Tilburg, The Netherlands)

08:00-09:00
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B10
BREAKFAST SEMINAR
Physics - New Technologies (FLASH, Lattice, Small Fields, ...)

BREAKFAST SEMINAR
Physics - New Technologies (FLASH, Lattice, Small Fields, ...)

Moderators: Antonella DEL VECCHIO (Director) (Milan, Italy), Thierry GEVAERT (Head of Medical physics) (Brussels, Belgium)
Coordinator: Ian PADDICK (London, United Kingdom)
08:00 - 09:00 Oxygen-guided radiotherapy (OGRT). Gianluca FERINI (Chief of Radiation Oncology Unit) (Viagrande, Italy)
08:00 - 09:00 FLASH and innovative / personalized fractionation schemes. Jean BOURHIS (Head of the Department of Radiation Oncology) (Lausanne, Switzerland)
08:00 - 09:00 Combined radiation / thermal dose models for hyperthermia + SRS. Iuliana TOMA-DASU (Head of Medical Radiation Physics Division) (Stockholm, Sweden)

08:00-09:00
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C10
BREAKFAST SEMINAR
SBRT for Genito-Urinary Tumors

BREAKFAST SEMINAR
SBRT for Genito-Urinary Tumors

Moderators: Nadia DI MUZIO (Director) (Milano, Italy), Barbara JERECZEK-FOSSA (Associate Professor - Head of Division) (MILAN, Italy)
Coordinator: Ciro FRANZESE (Milano, Italy)
08:00 - 09:00 SBRT for primary prostate cancer: the time is now. Barbara JERECZEK-FOSSA (Associate Professor - Head of Division) (MILAN, Italy)
08:00 - 09:00 Focal boost with stereotactic radiotherapy in prostate cancer. Linda KERKMEIJER (Radiation oncologist) (Nijmegen, The Netherlands)
08:00 - 09:00 SBRT for primary renal cell carcinoma: A novel tool in the toolbox. Alexander MUACEVIC (Director) (Munich, Germany)

09:15
09:15-10:15
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A11
PLENARY SESSION
Special Topics: ISRS Guidelines & ISRS Certification Programme

PLENARY SESSION
Special Topics: ISRS Guidelines & ISRS Certification Programme

Moderators: Laura FARISELLI (director) (milan, Italy), Marc LEVIVIER (Chef de Service) (Lausanne, Switzerland), Arjun SAHGAL (Professor) (Toronto, Canada)
Coordinator: Arjun SAHGAL (Toronto, Canada)
09:15 - 10:15 Recurrent glioblastomas. Valentina PINZI (senior assistant) (Milan, Italy)
09:15 - 10:15 Vestibular Schwannomas – Koos I-II. Anne BALOSSIER (Dr) (Marseille, France)
09:15 - 10:15 Vestibular Schwannomas – Koos IV. Constantin TULEASCA (Staff neurosurgeon, senior lecturer) (Lausanne, Switzerland)
09:15 - 10:15 Pediatric SBRT. Erin MURPHY (Radiation Oncologoy) (Cleveland, USA)
09:15 - 10:15 ISRS Certification Programme. Ian PADDICK (Consultant Physicist) (London, United Kingdom)

10:15 - 10:45 COFFEE BREAK AND EXHIBITION
10:45
10:45-12:00
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A13
PLENARY SESSION
Special Topic: Brain Metastases

PLENARY SESSION
Special Topic: Brain Metastases

Moderators: Francesco DI MECO (Head Department of Neurosurgery) (Milan, Italy), Lucia SCHWYZER (Senior Physician) (Aarau, Switzerland), Paul SPERDUTO (Radiation Oncology) (Durham, USA)
Coordinator: Paul SPERDUTO (Durham, USA)
10:50 - 11:07 Re-irradiation. Steve BRAUNSTEIN (Faculty) (San Francisco, USA)
11:07 - 11:24 Pre-irradiation before surgery. Stuart BURRI (Chairman) (Charlotte, USA)
11:24 - 11:41 Pros & Cons: Staged SRS versus fractionation in large brain metastases. Eduardo LOVO IGLESIAS (Brain and Spine Radiosurgery Program) (San Salvador, El Salvador)
for “staged”
11:41 - 12:00 Pros & Cons: Staged SRS versus fractionation in large brain metastases. Giuseppe MINNITI (Consultant) (roma, Italy)
for “fractionation”

12:00
12:00-13:00
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A14
PARALLEL SESSION
Skull-base Societies Session: Combined Approaches in Skull-base Tumors

PARALLEL SESSION
Skull-base Societies Session: Combined Approaches in Skull-base Tumors

Moderators: Paolo CAPPABIANCA (Italy), Marc LEVIVIER (Chef de Service) (Lausanne, Switzerland), Davide LOCATELLI (Professor, Head neurosurgery dpt.) (Varese, Italy)
Coordinator: Giovanni DANESI (Bergamo, Italy)
12:00 - 13:00 Vestibular Schwannomas. Roy Thomas DANIEL (Médecin Chef, Associate Professor) (lausanne, Switzerland)
12:00 - 13:00 Pituitary tumors. Douglas KONDZIOLKA (New York, USA)
12:00 - 13:00 Paragangliomas. Giovanni DANESI (head of Dept.) (Bergamo, Italy)

12:00-13:00
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B14
PARALLEL SESSION
SBRT for Pancreatic and Liver Tumors

PARALLEL SESSION
SBRT for Pancreatic and Liver Tumors

Moderators: Nicolaus ANDRATSCHKE (Consoultant) (Zürich, Switzerland), Marta SCORSETTI (Director Department) (Rozzano-Milan, Italy)
Coordinator: Marta SCORSETTI (Rozzano-Milan, Italy)
12:00 - 13:00 The role of SBRT for hepatocellular carcinomas. Alejandra MENDEZ-ROMERO (Medical Staff) (Rotterdam, The Netherlands)
12:00 - 13:00 Liver metastases treated with SBRT: results and comparison with other local treatments. Tiziana COMITO (Rozzano, Italy)
12:00 - 13:00 SBRT for inoperable and borderline resectable pancreatic cancer. Anna BRUYNZEEL (Amsterdam, The Netherlands)

13:00
13:00-14:00
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A15b
SPONSORED LUNCH SYMPOSIUM

SPONSORED LUNCH SYMPOSIUM

LUNCH - EXHIBITION
14:00
14:00-15:00
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A16
ORAL PRESENTATIONS
Skull-base Societies Session: Vestibular Schwannomas

ORAL PRESENTATIONS
Skull-base Societies Session: Vestibular Schwannomas

Moderators: Maurizio IACOANGELI (President) (Italy), Jeroen VERHEUL (neurosurgeon) (Tilburg, The Netherlands)
14:00 - 14:10 #29389 - OP01 Multisession compared to single-session radiosurgery to preserve the hearing in patients affected by sporadic vestibular schwannoma. The results from a prospective randomized clinical trial.
OP01 Multisession compared to single-session radiosurgery to preserve the hearing in patients affected by sporadic vestibular schwannoma. The results from a prospective randomized clinical trial.

Objective. Radiosurgery for acoustic schwannoma is continuously increasing.

The attention is actually focusing on the hearing function sparing.

The aim of the present study is to investigate about potential advantages of multisession radiosurgery(mRS) compared to single session radiosurgery(sRS) in terms of hearing preservation in patients with serviceable hearing.

Patients and methods. The primary end-point of this prospective, randomized clinical trial is the difference in term of hearing preservation between patients treated with mRS and sRS because of a sporadic acoustic neuroma.

The conditions for patient eligibility are:

-sporadic acoustic neuroma diagnosis.

-Age≥18 years old

-KPS≥70

-Serviceable hearing: class A/B (AAOHNS classification)

-Written consent

All the enrolled patients are clinically, radiologically and audiometrically evaluated.

The volumetric analysis of the tumor is always performed.

Results. One-hundred-eight patients were enrolled and treated according to the study protocol.

Three patients refused the treatment after the randomization process and in 4 cases the eligibility criteria were not satisfied, 101 patient were therefore evaluated.

Forty-seven patients had a 12Gy sRS on a mean volume of 1.9cc; 54 patients had a mRS (18Gy/3 fractions) on mean volume of 1.7cc.

After a mean follow-up period of 34 months (range 4-97 months) 59 patients (58%) maintained a serviceable hearing. No significant differences were observed between sRS and mRS in term of hearing preservation. Particularly, forty-two patients (42%) experienced a hearing deterioration (class C and D); with 21 patients undergoing sRS and 21 mRS. The most important predictor factor was the pre-treatment haring status. The treatment related toxicity was always mild. The most common side effect was a transient balance impairment.

Along all the observation period three patients required surgery because of tumor progression. One patient had an excellent surgical outcome (HB1); one had an intermedium outcome (HB2-3),while the third developed a complete facial palsy (HB4). In all these cases, the histology confirmed the radiological diagnosis of schwannoma.

Conclusions. At our knowledge, the present clinical trial is the first one comparing two different radiosurgical regimens in terms of hearing sparing.

While we are waiting for a longer follow-up period, the preliminary results from this study suggest that mRS has no advantages compared to sRS in terms of hearing preservation.

Our preliminary results suggest that the better is the auditory function at the moment of the treatment, the more probable is the hearing preservation.

The volumetric analysis confirms the very good post radiosurgery tumor control rate.


Marcello MARCHETTI (Milano, Italy), Valeria CUCCARINI, Irene TRAMACERE, Irene CANE, Francesco GHIELMETTI, Sara MORLINO, Valentina PINZI, Cecilia IEZZONI, Laura FARISELLI
14:10 - 14:20 #29314 - OP02 - WITHDRAWN - TUMOR CONTROL AND HEARING PRESERVATION AFTER GAMMA KNIFE RADIOSURGERY FOR VESTIBULAR SCHWANNOMAS IN NEUROFIBROMATOSIS TYPE 2.
OP02 - WITHDRAWN - TUMOR CONTROL AND HEARING PRESERVATION AFTER GAMMA KNIFE RADIOSURGERY FOR VESTIBULAR SCHWANNOMAS IN NEUROFIBROMATOSIS TYPE 2.

OBJECTIVE : One of the first-line treatment options for small to medium-large VSs is radiosurgery. Although radiosurgery shows excellent results in sporadic VS, its use in NF2- related VS is still a topic of debate. The aim of this study was to evaluate long-term tumor control, hearing preservation rates, and assess factors which could predict these outcomes. Also tumors which underwent retreatment following GKRS was evaluated.

METHODS : This was a Single institute retrospective analysis of all cases of NF2 associated VS fulfilling Manchester criteria who underwent GKRS between 2009 and 2019.The median marginal dose was 12 Gy. Patients’ case records,radiology and audiometric charts were analysed. Patients with follow up of less than one year were excluded. Loss of tumor control was defined as greater than 10% increase in volume in more than one follow up imaging or the need for retreatment in the form of repeat GKRS or surgery.Actuarial tumor control rates were estimated using the Kaplan-Meier curves. Trigeminal and facial nerve function were assessed before and after treatment.Hearing preservation rates waere assessed at last follow up.

RESULTS: A total of 85 patients with 133 VSs were included in the study. The mean age was 29.8 years(12-65 years).The tumor was more common in males with M: F ratio of 11:6. 71 patients had a median follow up duration of 34.1 months(14- 111 months).57 tumors(49.6%) showed tumor regression, 35 tumors(30.4%) showed stable disease and 23 tumors progressed in size(15%) at last follow up.Actuarial tumor control rates in NF2 patients after 1, 3, 5 and 9 years were 95%, 79%, 75%, and 55% respectively with overall tumor control rate being 85%.Serviceable hearing preservation rate at last follow up was 61.7% with total hearing preservation rate of 66.9%.There was no treatment related mortality.One patient developed transient trigeminal neuralgia.Facial nerve function worsened in 4 patients(3.3%) two of whom received secondary GKRS.4 patients(5 tumors) underwent retreatment with GKRS at a median duration of 27.6 months(19-36 months) following first GKRS.All tumors had regressed in the follow up with one case of worsening of hearing grade and new onset facial palsy.2 patients required surgery following GKRS.

CONCLUSIONS :This is the largest radiosurgical series of NF2 associated VS reported till date.GKRS provides a high rate of long-term local tumor control with a low risk of neurological injury for patients with these tumors.The need for retreatment with GKRS although low,is associated with good tumor control and lesser complications.


Bhavya PAHWA (New Delhi, India), Gour Surya SRI KRISHNA, Deepak AGRAWAL
14:20 - 14:30 #30185 - OP03 An update on the influence of the pretreatment growth rate on the efficacy of gamma knife radiosurgery for vestibular schwannomas.
OP03 An update on the influence of the pretreatment growth rate on the efficacy of gamma knife radiosurgery for vestibular schwannomas.

Introduction

Prognostic factors of tumor control after Gamma Knife radiosurgery (GKRS) for vestibular schwannomas (VS) remain largely unknown. Four years ago, we reported that the growth rate of VS before GKRS is indicative of the probability that radiosurgery achieves tumor control. These findings may have important implications for treatment strategies and may lead to advise for either microsurgery or higher marginal doses for fast-growing tumors. The objective of this study is to validate the previously obtained results in the correlation between the pretreatment growth rate and tumor control after GKRS, using an updated and significantly larger dataset.

 

Methods

Patients treated between 2002 and 2015 were identified, who had a pretreatment scan available of at least 6 months prior to treatment and had at least 2 years of follow-up after GKRS. Tumor volumes before, at, and after treatment were assessed. GKRS was performed in a uniform way with a marginal dose between 11 and 13 Gy. Treatment failure was defined as radiological progression beyond 2 years after GKRS. Volume doubling times (VDTs) before treatment were correlated with the observed tumor control rates and volumetric responses after treatment. Kaplan-Meier and Cox regression analyses were employed to investigate the effect of the VDT on the treatment response.

 

Results

A total of 402 patients met the inclusion criteria. The median follow-up time is 85 months. In this cohort, 50 patients showed a radiological failure. The resulting 5- and 10-year tumor control rates are 92.7% and 83.2%, respectively. The calculated VDTs vary between 3 and 344 months, with a median VDT of 15 months. Splitting the cohort into two sub-cohorts using the median VDT, results in 5- and 10-year control rates of 87.1% and 74.3% for the faster growing tumors, and 97.8% and 91.8% for the slower growing tumors, respectively (log-rank, p<0.001) (Figure 1). The Cox regression analyses demonstrate a statistically significant effect (p=0.009) of the pretreatment growth rate on tumor control, thereby enabling the probability calculation of obtaining tumor control after GKRS.

 

Conclusion

This updated and more extensive study clearly verifies our earlier findings: the pretreatment growth rate correlates with the observed tumor control after GKRS. More specifically, it denotes that fast-growing tumors are less likely to obtain tumor control. Our Cox regression model enables the calculation of the risk at treatment failure on an individual basis. Furthermore, these results might justify alterations in the management of VS.


Patrick LANGENHUIZEN, Patrick LANGENHUIZEN (Tilburg, The Netherlands), Stefan CORNELISSEN, Sammy SCHOUTEN, Henricus KUNST, Peter DE WITH, Jeroen VERHEUL
14:30 - 14:40 #29961 - OP04 Combined approaches for large vestibular schwannomas in a series of 50 consecutive cases.
OP04 Combined approaches for large vestibular schwannomas in a series of 50 consecutive cases.

Background: The 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 of a new treatment paradigm of combined approach with microsurgery and GKRS,
aiming at optimal functional outcome for the facial and cochlear nerves in patients with large VS (i.e. Koos grade IV).
 Data pertaining to patient characteristics, surgical and dosimetric features and outcome were collected prospectively at time of treatment and during the follow-up course. We report our long-term follow-up using this approach on 50 consecutive patients.  

Results: The mean presurgical tumor volume was 11.25 cm3 (1.47-34.9) and mean follow-up after surgery was 39.4 months (range 6-102).All cases had normal facial nerve function (HB I) before surgery, except for one who was in HB IV, and one in HB III. Postoperative status showed normal facial nerve function (House-Brackmann grade I) in all patients, with the exception of the one who was in HB III preoperatively and which remained in HB III after surgery. In a subgroup of 29 patients in which cochlear nerve preservation was attempted at surgery (patients with residual hearing before surgery), 27 of them (93.1%) retained residual hearing. 19 patients had normal hearing (Gardner-Robertson class 1) before surgery, and 16 (84.2%) 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 3.3 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 (range 11-12, median 12 Gy). Four patients were considered a failure and benefitted from a second combined approach in 3 cases and only GKRS, in one case. Three patient benefitted from a VP shunt.  

Conclusion: Our data suggest 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 GKRS alone in small- and medium-size VS. 


Marc LEVIVIER (Lausanne, Switzerland), Constantin TULEASCA, Mercy GEORGE, Raphael MAIRE, Luis SCHIAPPACASSE, Roy Thomas DANIEL
14:40 - 14:50 #29399 - OP05 Hypofractionated Stereotactic Radiosurgery for Koos Grade IV Vestibular Schwannomas.
OP05 Hypofractionated Stereotactic Radiosurgery for Koos Grade IV Vestibular Schwannomas.

Objectives: The Koos classification is frequently used for vestibular schwannomas (VS), and Koos grade IV VS are large tumors with brainstem and cranial nerve displacement. These giant tumors adversely affect patients, and the goal of treatment is to achieve oncological control against a good postoperative functional outcome in facial or cochlear nerves. Although microsurgical resection is suggested as the treatment of choice, a tendency towards hypervascularity and adhesion to neurological structures should be kept in mind. Hypofractionated Gamma Knife radiosurgery (hf-GKRS) has been suggested as an alternative for VS. This retrospective, single-center study evaluated patient outcomes of upfront hf-GKRS for Koos grade IV VS.

Methods: Twenty-two patients (12 males and 10 females) were treated with upfront hf-GKRS. The median age of the patients was 48 years (range, 27-74 years). The most common indication for hf-GKRS was patient preference (22.7%). Prior to hf-GKRS, 11 patients (50%) had hearing loss (defined as Gardner-Robertson Grade III and IV), one patient (4.6%) had House-Brackmann Grade II facial palsy, and four patients (18.2%) had trigeminal nerve dysfunction. The median time from diagnosis to hf-GKRS was 3 months (range, 0-48 months). The median tumor volume was 10.55 cm3 (range, 6.2-18.6 cm3). The most commonly used fractionation scheme was 3x6 Gy (81.8%).

Results: The median follow-up was 23 months (range, 17-38 months), and tumor control was achieved in all patients, with regression in 11 patients (50%). A serviceable hearing was retained in all 11 patients at the last follow-up. Adverse radiation effects were observed in three patients (13.6%), with one patient having brainstem edema and two patients having trigeminal neuralgia. All patients were managed with medical treatments. One patient (4.6%) had new-onset hydrocephalus and underwent ventriculoperitoneal shunting.

Conclusions: We have demonstrated that hf-GKRS can be an effective and safe alternative to surgery in select patients with Koos IV VS. Further, well-designed studies are required to establish the long-term efficiency of hf-GKRS in the management of Koos IV VS. 


Yavuz SAMANCI (Istanbul, Turkey), Mustafa BUDAK, Fatih KARAKÖSE, Selçuk PEKER
14:50 - 15:00 #30085 - OP06 20-year follow up of neuromas and meningiomas after linac-based srs.
OP06 20-year follow up of neuromas and meningiomas after linac-based srs.

   Intracranial tumors have been traditionally treated with surgery. Novel RT techniques, such as stereotactic radiosurgery (SRS), have expanded therapeutic options in this field. As the literature reports high control rates and limited toxicity after stereotactic radiosurgery for intracranial neuromas and meningiomas SRS has been established as an appealing option for both clinicians and patients. Although radiosurgery has been traditionally performed as Gamma Knife or Cyberknife surgery nowadays widely available linac-based approaches have gained popularity.

   In this single institution study, we present the results of linac-based stereotactic radiosurgery after a long follow up of patients treated for benign intracranial neuromas and meningiomas focusing on local control and toxicity. Thirty-four consecutive patients were treated during 2000-2004 with primary or postoperative SRS for tumors less than 3.5 cm in maximum diameter.

   Stereotactic radiosurgery was performed using the 6 MV beam of a non-dedicated Elekta SL-18 linear accelerator converted for radiosurgery with the attachment of an isocentric subsystem (Phillips SRS200XK). Non-coplanar arc irradiation was delivered with circular collimators ranging in diameter from 10-30 mm. A stereotactic headring fixation was used. A treatment plan was achieved using 1-8 isocenters. Neuroma patients were treated with 11-12 Gy, while larger doses of 12-15.5 Gy were given to meningioma patients. Combining a different number, span and weight of noncoplanar arcs, as well as weight and collimator size of each isocenter used, high conformality of the treatment dose to the borders of the tumor was established.    Since nervous tissue is a late responding tissue, a long follow up is required after radiosurgery for benign intracranial tumors to assess not only tumor control but also RT-related toxicity. SRS patients were followed up twice yearly for the first year and annually thereafter. Imaging studies as well as cranial nerve assessment were mandatory. Clinical follow up was obtained from the patients or their referral doctors.

   After twenty years 26 patients are still in follow up and high rates of local control are documented with no cases of treatment failure Tumor shrinkage was observed in 61,5% and 58%  of neuroma and meningioma patients, respectively. Toxicity was minimum with no patient developing new permanent facial or trigeminal neuropathy.

   Overall, our study confirms the efficacy and safety of linac-based stereotactic radiosurgery after extended follow up for neuroma and meningioma patients.


George PISSAKAS (Athens, Greece), Paraskevi GEORGOLOPOULOU, Maria Angeliki KALOGERIDI, Kleanthi DOUKAKI, Efthimios ANDRIOTIS, George ARCHONTAKIS, Nikolaos KORDIOLIS

14:00-15:00
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B16
ORAL PRESENTATIONS
Physics (1)

ORAL PRESENTATIONS
Physics (1)

Moderators: Georgios KRITSELIS (PRIVATE PRACTICE) (ATHENS, Greece), Giacomo REGGIORI (Medical Physicist) (Milan, Italy)
14:00 - 14:10 #30153 - OP07 Benchmarking Tests of Contemporary SRS Platforms: Have Technological Developments Resulted in Improved Treatment Plan Quality?
OP07 Benchmarking Tests of Contemporary SRS Platforms: Have Technological Developments Resulted in Improved Treatment Plan Quality?

Introduction

The technological evolution of SRS equipment, where the demands of conformity, gradient and accuracy are at its highest, is significant. Six years on from the 2016 UK benchmarking study [Eaton et al], new technology poses the question “have technological improvements led to a corresponding improvement in treatment plans?”. This benchmarking study assesses the capabilities of the following platforms which were selected as ‘state of the art’ in 2022: Gamma Knife Icon with Lightning inverse planning (GK), Cyberknife S7 with M6 MLC, BrainLab Elements (Elekta VersaHD and Varian TrueBeam), Varian Edge with HyperArc (both 6X-FFF and 10X-FFF), Zap-X.

Methods and Materials

Six cases (two multiple metastasis cases, four benign targets) were used from the previous study. In order to reflect the evolution of the increased number of metastases treated per patient, a case with 14 targets was added. 28 targets amongst the seven patients ranged from 0.02cc to 7.2cc in volume.

Participating centres were sent DICOMRT files containing images, target contours and potential OARs for each treatment plan. They were asked to plan each treatment to the best of their ability using experienced staff (defined as at least two years’ experience with the relevant platform). 

While some variation in local practice was allowed (eg. the use of margins), groups were asked to prescribe a specified dose to each target and tolerance doses to organs at risk were agreed in advance.

Parameters used for comparison between the plans, included coverage, selectivity, Paddick Conformity Index (PCI), Gradient Index (GI), R50%, Efficiency Index, doses to OARs, estimated planning and estimated treatment time.

Results

Mean coverage for all targets ranged from 98.2% (Brainlab/Elekta) to 99.7% (Hyperarc 6X). PCI values ranged from 0.722 (Zap-X) to 0.900 (CyberKnife). GI ranged from a mean of 3.15 (Zap-X), representing the steepest dose gradient to 5.08 (HyperArc 10X). The GI appeared to follow a trend with beam energy, with the lowest values from the lower energy platforms (Zap-X; 3MV, GK; 1.25MeV) and the highest value from the highest energy (HyperArc 10X).

R50% values (excluding case 7), which are combination of conformity and gradient indices, had a minimum mean value of 3.65 (GK) and a maximum mean value of 4.76 (Hyperarc 10X). Treatment times were lowest with modified linacs.

Conclusion

Compared with earlier studies, newer equipment appears to deliver higher quality treatments. CyberKnife and Linac platforms appear to give better conformity while lower energy platforms give better dose gradient.


Ian PADDICK (London, United Kingdom), James BEDFORD, Peter FILATOV, Judith MOTT, Gavin ORCHIN, Diana GRISHCHUK, David EATON
14:10 - 14:20 #29586 - OP08 Evaluation of a novel dose optimization software Leksell Gamma Knife Lightning – comparison of treatment plans for 40 challenging clinical cases.
OP08 Evaluation of a novel dose optimization software Leksell Gamma Knife Lightning – comparison of treatment plans for 40 challenging clinical cases.

Purpose: There are three approaches in treatment planning for Leksell Gamma Knife Icon: 1) manual, 2) inverse planner for Icon and 3) Lightning dose optimization. In the first two methods a reasonable number of isocenters are being placed inside the target volume with relatively small overlap. Various weighting factors and hybrid isocenters (mixture of 4, 8, 16 mm collimators together with blocks) can be used. In opposite the Lightning is using a very large number of isocenters with a very large overlap. It can be described as a “painting” of dose distribution due to very small position change in individual isocenters.

Materials and Method: Fourty patients (10 meningiomas, 10 acoustic schwannomas, 10 pituitary adenomas, 10 metastases) were selected for comparison. Patients with larger treatment volumes (1.8 – 23.0 cm3, median 7.6 cm3) and challenging cases were selected. Following parameters were used to assess benefits in new treatment planning approach: target mean dose, target coverage, selectivity, gradient index, Shaw conformity index, volume of 12 Gy, volume of 80% and 90% isodose, maximal dose to optic nerve, brainstem and cochlea, mean dose to cochlea and pituitary, beam-on time and number of isocenters used. Time for Lightning to calculate the treatment plan was also measured.        

Results: Extremely short time (14 – 108 s, median 35 s) was observed for calculation of all cases when using Lightning. With the same target volume coverage (median 0.99), Lightning used always more (16 - 86, median 41) isocenters to achieve the goal. Following percentages are given for medians to compare Lightning with former methods. Target mean dose was reduced by 5.7%, selectivity improved by 8.9%, gradient index improved by 0.2 %, Shaw conformity index improved by 8.7%, volume of 12 Gy was reduced by 5.2%, volume of 80% and 90% isodose increased by 9.1% and 5.0%, respectively. Doses to critical structures improved by 12.3% (optic), 8.9% (cochlea), 5.0% (pituitary). Beam-on time was reduced in the case of Lightning by 14.4%.   

Conclusions: Practically in all studied parameters Lightning dose optimization software was superior to former methods. It is capable to generate not even better plans in terms of dosimetry characteristics, lower doses to critical structures but also plans with shorter beam-on time.   

Keywords: Leksell Gamma Knife, inverse planning, dose optimization, Lightning

This study was supported by the Ministry of Health, Czech Republic - conceptual development of research organization (Na Homolce Hospital - NNH, project No. IG174701).


Josef NOVOTNY (Prague, Czech Republic), Lucie HAMACKOVA, Marketa FARNIKOVA, Roman LISCAK, Dusan URGOSIK
14:20 - 14:30 #29647 - OP09 Implementation of IAEA TRS 483 in small field dosimetry of Leksell Gamma Knife Icon – transition from IAEA TRS 398 to IAEA TRS 483.
OP09 Implementation of IAEA TRS 483 in small field dosimetry of Leksell Gamma Knife Icon – transition from IAEA TRS 398 to IAEA TRS 483.

Purpose: Traditional dosimetry calibration of small Leksell Gamma Knife (LGK) beams was based on IAEA TRS 398 protocol. New IAEA TRS 483 protocol is available since 2017. Contrary to TRS 398, new small field TRS 483 protocol takes into account non-standard conditions e.g. very small field size, specific geometry, phantom used for measurement and etc. The purpose of this study was to perform transition from TRS 398 to TRS 483.

Materials and Method: Two Elekta plastic spherical phantoms were used: 1) acrylonitrile butadiene styrene (ABS) and 2) Solid Water (SW). Special inserts were made in each phantom to accommodate PTW 31010 Semiflex ion chamber with sensitive volume 0.125 cm3 (used for absolute dose calibration) and PTW 60019 microDiamond detector with sensitive volume 0.004 mm3 (used for output factors (OF) measurement). PTW Unidos electrometer was used for both absolute and relative dosimetry. Both TRS 398 and TRS 483 protocols and both ABS and SW phantoms were used for absolute and relative dosimetry.

Results: The optimal conditions for dose rate measurement are in SW phantom and following TRS 483 protocol. SW phantom is almost water equivalent (and thus very small corrections need to be applied), better mimics real clinical situation (patient fixation in treatment position) and due to longitudinal ion chamber orientation minimizing stem effect. Other results showed following deviations compare to SW and TRS 483: -1.97%, -0.55% and -0.37% for ABS phantom and TRS 398, for ABS phantom and TRS 483 and for SW phantom and TRS 398, respectively. OF measurements with microDiamond in ABS phantom for 8 mm collimator showed -0.1% and 0.6% deviation to Monte-Carlo calculated vendor default values when using TRS 398 and TRS 483, respectively, for 4 mm 2.1% and 1.4% deviation for TRS 398 and TRS 483, respectively. OF measurements with microDiamond in SW phantom for 8 mm collimator showed -1.5% and -1.0% deviation when using TRS 398 and TRS 483, respectively, for 4 mm 2.1% and 1.4% deviation for TRS 398 and TRS 483, respectively.    

Conclusions: Re-calibration of LGK Icon was made based on TRS 483 protocol which better reflects small field dosimetry conditions. Relatively small (within 2%) deviations to existing calibration and default OF values were observed.

 

Keywords: small field dosimetry, IAEA TRS 483, Leksell gamma knife Icon

 

This study was supported by the Ministry of Health, Czech Republic - conceptual development of research organization (Na Homolce Hospital - NNH, project No. IG 141202).


Josef NOVOTNY (Prague, Czech Republic)
14:30 - 14:40 #29701 - OP10 Gantry triggered x-ray verification of patient positioning during single-isocenter stereotactic radiosurgery using ExacTrac Dynamic: increasing certainty of lesion localization.
OP10 Gantry triggered x-ray verification of patient positioning during single-isocenter stereotactic radiosurgery using ExacTrac Dynamic: increasing certainty of lesion localization.

1.       Introduction and purpose

 

Single-isocenter linac-based stereotactic radiosurgery (SRS) has emerged as a dedicated treatment option for multiple brain metastases. To do so, image-guidance for patient positioning and motion management is becoming very important. The purpose of this study was to analyze the translational and rotational intra-fraction errors during SRS, by applying surface-guidance coupled with gantry triggered stereoscopic x-ray verifications during the arc delivery. The benefits of such a positioning system were also assessed.



2.                  Materials and methods

 

Treatments were planned with non- coplanar dynamic conformal arcs for 24 patients corresponding to 93 brain lesions. Intra-arc positioning errors were measured using stereoscopic x-rays (ExacTrac Dynamic, BrainLAB, Munchen, Germany), triggered in the middle of every treatment arc (234 arcs in total). Couch corrections above 0. mm and 0.5° are always applied. Intra-arc positioning data was analyzed and compared to those of a previous study in our department, where intra-fraction stereoscopic x-rays were only taken after each couch rotation.



3.                  Results and discussion

 

Intra-arc errors ranged between 0 mm and 1.64mm for translations and 0° and 0.88° for rotations (Figure 1). Total 3D displacement ranged between 0.03 mm and 1.64mm. 95th percentiles of errors across all arcs delivered were 0.58mm, 0.47mm and 0.32mm for longitudinal, lateral and vertical displacements, and 0.46°, 0.27° and 0.43° for roll, pitch and yaw rotations respectively. Mean errors across all patients were 0.18mm, 0.07mm and 0.16mm for longitudinal, lateral and vertical displacements, and 0.13°, 0.12° and 0.11° for roll, pitch and yaw rotations (Table 1). 6 out of 24 patients showed at least one arc above the correction thresholds (0.7mm for translations, 0.5° for rotations), corresponding to 17 treatment arcs (7% of delivered beams). When compared to inter-beam errors measured after table rotation, the mean errors measured were considerably smaller (Figure 2), ranging from 38.2% (lateral) to 80% (longitudinal) reduction. 

 

 

4.                  Conclusions

 

Gantry triggered x-ray verification provides information of the real position of the patient during irradiation and allows verification of the couch corrections performed before every arc. When comparing inter-arc and intra-arc positioning errors, we could identify table rotation as an important source of patient motion. A beam-off strategy is to be considered when measured intra-arc errors are out of tolerance, as the frequency of corrections would not increase treatment times considerably. Intra-arc monitoring and correction with stereoscopic x-rays increases the certainty of lesion localization, making a 0 mm margin strategy possible.


Adrián GUTIÉRREZ (Brussels, Belgium), Thierry GEVAERT, Jelle SMEULDERS, Boussaer MARLIES, Tim EVERAERT, Anne-Sophie BOM, Cristina FERRO TEIXEIRA, Mark DE RIDDER
14:40 - 14:50 #30148 - OP11 Evaluation of the timing and quality of a reference beam model-based “short” commissioning.
OP11 Evaluation of the timing and quality of a reference beam model-based “short” commissioning.

Purpose and objective

Commissioning measurements are time-consuming and require high precision in execution. Reference Beam Models (RBM) consist of predefined Pencil Beam and Monte Carlo dose profiles that may dramatically reduce the number of measurements necessary to commission a beam. The purpose of this work was to evaluate the accuracy and robustness of using  the RBMs offered by BrainLab®(Munich, Germany) with the treatment planning system (TPS) Elements® for multiple brain metastases.

Materials and method

The 6MV and 10MVFFF beams of a TrueBeamSTX Linac were considered. The Linac was equipped with a HD120 MultiLeafCollimator (MLC) whose central leaves have a width of 2.5mm at isocenter.

A Beamscan water tank (PTW, Freiburg, Germany) was used with a SSD=900. Absolute dose was measured at isocenter with a Farmer-type calibrated ion chamber for a 10x10cm2 field. Profiles and PDDs were measured for 4 different MLC-defined square fields ranging from 5x5 to 220x220mm2. Output Factors were measured for the same fields and in the same set-up. A PTW MicroDiamond detector and a 0.125cc PTW Semiflex 3D ion chamber were used for all measurements. A comparison between these measurements and calculations performed in a virtual water phantom with MC-Elements and Acuros algorithms were performed.

Once the TPS was configured, some “simple” plans (i.e. without MLC) and 5 patients were planned with the Multiple Brain Metastases module and delivered. The dose distribution was verified with three different methods. The 2D fluence distribution was evaluated with Portal Dosimetry. The log-file reconstructed 3D dose distribution was evaluated with an indipendent algorithm (M3D, Mobius). The measured 3D dose distribution was evaluated with the octavius detector.

Results     

The total time required for the commissioning measurements was less than 6 hours. The best agreement between measured and modeled values both for OFs and profiles was obtained selecting a spot size of 0.4mm and 0.Xmm for 6MV and 10MVFFF beams respectively (figure 1). Calculated OFs were within 1.6% for all field sizes except for the 5x5mm were it was 4.8% (figure 2). The 3%-3mm 3DGamma >96.3% (96.3%-99.8%) for the “simple” plans. Gamma values for the 5 clinical plans were 99.5%-100% for Portal Dosimetry, 99.8%-100% for the M3D calculation and 97.3%-99.1% for the Octavius4D measurements.    

Conclusion

Machine commissioning times are dramatically reduced and compatible with clinical practice. The configuration and selection of the RBM is simple and intuitive. Good agreement between measured and calculated dose distributions was observed down to very small field sizes.


Giacomo REGGIORI (Milan, Italy), Francesco LA FAUCI, Pasqualina GALLO, Lucia PAGANINI, Francesca LOBEFALO, Andrea BRESOLIN, Pietro MANCOSU, Pierina NAVARRIA, Elena CLERICI, Luisa BELLU, Marta SCORSETTI, Stefano TOMATIS
14:50 - 15:00 #29992 - OP12 A comparative dosimetric study of Pencil Beam, Acuros XB, and Monte Carlo algorithms for stereotactic body radiosurgery of lung lesions.
OP12 A comparative dosimetric study of Pencil Beam, Acuros XB, and Monte Carlo algorithms for stereotactic body radiosurgery of lung lesions.

Introduction: The IGRT VMAT dose delivery allows more precise dose deposition and superior local control. The quality of these techniques can be enhanced by more accurate dose calculation such as Monte Carlo Algorithm (MC). The purpose of this study is to compare three commercially available dosimetric algorithms in 5 patients with Non Small Cell Carcinoma (NSCCA) and validate and compare with an in-house heterogeneous phantom mimicking the lung tumors.

Materials and methods: The GTVs and PTVs  (5mm margin) were generated for 5 anonymized patients with NSCCA. Treatment plans with 3 co-planar VMAT arcs were made to deliver 50Gy in 5 fractions to PTVs using MC and PB. The plans then exported to Eclipse planning system (EPS) and dose were recalculated using the Acuros XB (AXB) algorithm using the same leaf sequences and MUs for each VMAT beam and compared to the MC and PB results. Furthermore, an in-house heterogeneous phantom was created consisted of a Sun Nuclear diode phantom placed symmetrically between 7cm Styrofoam (HU, -800) and 3 cm solid water, on top and bottom simulating a lung cancer treatment. 3 VMAT arcs were used to deliver 16Gy to three PTVs contoured on the phantom with volumes of 4, 2, and 0.4ml using both the MC and PB dosimetric algorithms. The plans exported to EPS and the dose was recalculated using the AXB algorithm. The mean dose to the PTVs was compared with the measured dose in the phantom for each dosimetry algorithm. 

 

Results: The patients’ dose was significantly overestimated by PB when compared with MC. There is a statistically significant difference between the mean, maximum PTV dose, the conformity index, and total MUs between the PB and MC, (p-Values 0.008, 0.007, 0.03, 0.02, respectively). The mean measured and calculated dose in the phantom with MC for the 3 PTVs was within 1.1% (0.18Gy, p-Value 0.77). In comparison, the PB resulted in a statistically significant dose difference from the in-phantom measured dose (10.44%, 1.78Gy, p-Value 0.002). The mean absolute dose difference between MC and AXB was also statistically significant (4.9%, p-Value 0.01).

 

Conclusions: When compared to MC, the PB and AXB overestimated the lung tumor dose by 10.44% and 4.9%, respectively. We found the in-house phantom to be useful for this study. In the absence of MC algorithm, the limitations of the PB and AXB for lung cancer treatments should be kept in mind. Further study is warranted.

 


Javad RAHIMIAN (Los Angeles, USA), Juying ZHANG, Justin P. VINCI, Michael COHEN

14:00-15:00
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C16
3D Skull-base Anatomy for Safe Radiosurgery (1)

3D Skull-base Anatomy for Safe Radiosurgery (1)

Coordinator: Siviero AGAZZI (Tampa Florida, USA)
Keynote Speaker: Siviero AGAZZI (Tampa Florida, USA)

15:00
15:00-16:00
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A17
ORAL PRESENTATIONS
Skull-base Societies Session: Meningiomas

ORAL PRESENTATIONS
Skull-base Societies Session: Meningiomas

Moderators: Lina Raffaella BARZAGHI (Consultant) (MILAN, Italy), Michael SCHULDER (Vice Chair, Neurosurgery) (Lake Success, NY, USA)
15:00 - 15:10 #30208 - OP13 Radiosurgery for skull base meningiomas: outcomes from over 3500 cases – update a comparative analysis with anatomical nuances.
OP13 Radiosurgery for skull base meningiomas: outcomes from over 3500 cases – update a comparative analysis with anatomical nuances.

Objective: Skull base Meningiomas are the most frequent benign tumours treated with Gamma Knife Radiosurgery . However, the assessment of its efficacy and safety in slow growing tumours is an ongoing process, requiring analysis of long-term results. This study involves the experience of several European Gamma Knife Centres. We report on the efficacy of radiosurgery for the treatment of skull base Meningiomas, clinical and radiological control and side effects

Methods: From 15 participating centers, we performed a retrospective observational analysis of a cohort of 3752 benign meningiomas treated with GKRS. All were treated with Gamma Knife radiosurgery at least 5 years before assessment for this study. Clinical and imaging data were retrieved from each center and uniformly entered into a database by 1 author. A statistical analysis is presented.

Results: 3451 patients harbouring 3752 meningiomas treated in fifteen institutions recruited were evaluated. The median age was 56 years (range 6 - 89 years). The median tumour volume was 5.20 ccm (range
0.5 - 85 ccm) and tumour margin dose to the 50 % isodose line 13.5 Gy (range 3 - 45 Gy). The median radiological follow-up was 61 months, but detailed results were only available for 3259 meningiomas (86.8 %). The volume of treated tumours decreased in 1753 lesions (54 %) did not change in 1305 lesions (40 %) and increased in 200 lesions (6 %). The temporary morbidity rate after GKRS was 5.3 % and the permanent morbidity rate was 5.6 %. The actuarial control rate was 97.9 % at 5 years post Radiosurgery.

Conclusions: Radiosurgery is a safe and not invasive method of treatment of skull base meningiomas and the large number analysed confirms a high tumour control and low morbidity rate even after a long-term follow-up period.


Santacroce ANTONIO (Munich, Germany)
15:10 - 15:20 #29321 - OP14 PERIOPTIC MENINGIOMAS TREATED WITH CYBERKNIFE RADIOSURGERY (1 - 5 SESSIONS): CLINICAL RESULTS.
OP14 PERIOPTIC MENINGIOMAS TREATED WITH CYBERKNIFE RADIOSURGERY (1 - 5 SESSIONS): CLINICAL RESULTS.

Single session radiosurgery has established itself as an effective therapeutic modality in the primary or postoperative treatment of intracranial meningiomas. However, the treatment of lesions located less than 3 mm from the anterior optic pathway, represents a radiosurgical challenge due to the poor tolerance of these structures to high doses of radiation. In our study 42 patients with perioptic meningiomas were retrospectively treated with radiosurgery using Cyberknife in 1, 3 and 5 sessions, between April 2011 and April 2019. 3 patients (7%) had received previous radiotherapy and 25 patients (60%) had undergone surgery. In 62% of the cases, the lesions surrounded the anterior optic pathway, with no separation distance. 27 patients (64%) had visual impairment prior to treatment and 11 patients (26%) had involvement of other cranial nerves. 37 patients (88%) were treated in 5 sessions with a median tumor volume of 11.5 cc (0.14-37 cc). 34 of these patients received 25 Gy (5x5Gy) and one patient diagnosed with grade II meningioma received 30 Gy (5x6Gy). The other two patients, previously radiated, received 23Gy (5x4.6 Gy) and 20 Gy (5x4 Gy), respectively. 3 patients (7%) were treated in 3 sessions of 7 Gy (21 Gy) and 2 patients (5%) in a single session of 14 Gy with a median tumor volume of 6.2 cc (0.8-7.6 cc). The median tumor coverage with the prescription isodose was 98% and the median homogeneity and conformity index was 1.2 in both cases. The maximum dose in the optic pathway did not exceed 25 Gy in 5 sessions, 13 Gy in 3 sessions, and 7.7 Gy in a single session. The median clinical follow-up after treatment was 35 months (6-84 months) with MRI and campimetry. 18 patients (43%) experienced tumoral reduction and 23 patients (55%) presented stability. Only one patient had marginal progression and was surgically rescued. 19 patients (45%) had visual improvement after treatment, 21 patients (50%) remained clinically stable and two patients experienced worsening, one of them in the context of progression and the other already had previous symptoms and a bulky lesion compressing the optic pathway. Conclusions: This study shows that hypofractionated radiosurgery is a safe alternative, with excellent local control results and very low toxicity in the treatment of meningiomas whose proximity to the anterior optic pathway prevents single-dose treatments. However, a longer follow-up is necessary to fully validate these results.


Morena SALLABANDA (Madrid, Spain), Kita SALLABANDA
15:20 - 15:30 #29895 - OP15 Single-session stereotactic radiosurgery for large parasellar meningiomas.
OP15 Single-session stereotactic radiosurgery for large parasellar meningiomas.

Background

Meningiomas in close proximity to the optic pathway are commonly candidates for microsurgical decompression. More so large perioptic meningiomas. However, microsurgery itself imposes risk to vision and the larger the tumor the more the risk and lesser possibility of postoperative visual recovery. Fractionated radiotherapy is usually reserved for such cases.

 

Objective

The purpose of this study is to assess the long-term efficacy and safety of single-session stereotactic radiosurgery for large (10 cc or more) perioptic intracranial benign meningiomas.

 

Patients and methods

In this retrospective study we included 175 patients with large perioptic benign meningiomas (³ 10 cc) who were treated by single-session SRS. Perioptic meningiomas were defined as meningiomas touching, compressing or within 3 mm of the optic pathway. The median tumor volume was 15 (10-57.3 cc (IQR 8.4 cc)). The median prescription dose was 12 Gy (9-14 Gy (IQR 1 Gy)).

 

Results

The median follow up period was 72 months (13-217 months (IQR 65 months)). The tumor control rate was 92%. The PFS at 5- and 10- years was 97% and 80%. Favorable (better/stable) visual outcome was reported in 169 patients (97%) and unfavorable (worse) outcome in 6 patients (3%). Temporary adverse radiation effects were observed in 21 patients (12%) but only 7 (4%) were symptomatic. Sixty-three patients had a blind/non-useful eye according the pre-treatment visual field examination. Visual improvement was observed in blind/non-useful eye in 17 patients (27%) while vision remained unchanged in 46 patients (73%). Ocular nerve palsy improved in 36 patients (61%). Tumor shrinkage was not a prerequisite for cranial nerve improvement.

 

Conclusion

Stereotactic radiosurgery provides an effective and safe treatment option for large perioptic meningiomas.


Amr ELSHEHABY (CAIRO, Egypt), Wael A REDA, Khaled ABDEL KARIM, Reem EMAD ELDIN, Ahmed NABEEL, Sameh ROSHDY
15:30 - 15:40 #30024 - OP16 Postoperative radiosurgery in patients with meningiomas: improved planning using 68Ga-DOTATATE PET.
OP16 Postoperative radiosurgery in patients with meningiomas: improved planning using 68Ga-DOTATATE PET.

 

ABSTRACT

Background: Patients with meningiomas are typically treated with maximal safe surgical resection. After subtotal resection or at the time of tumor recurrence, stereotactic radiosurgery (SRS) is often used as the treatment of choice. While contrast-enhanced magnetic resonance imaging (MRI) is typically used for SRS target delineation, differentiating tumor growth from postoperative change can be challenging. 68Ga-DOTATATE, a positron emission tomography (PET) radiotracer targeting the somatostatin receptor type 2 (SSTR2), has been shown to be a reliable biomarker of meningiomas.

Objective: The aim of this study was to evaluate the impact of 68Ga-DOTATATE on treatment planning in patients who had previously undergone meningioma resection.

Methods: We present a consecutive case series of 13 patients with histologically-proven meningioma who received a 68Ga-DOTATATE PET between April 2019 and April 2021. Treatment planning was done at first using MRI only. The DOTATATE-PET images were then used to assess the accurate identification of tumor.

Results: Ten of the patients had WHO grade 2 meningioma and three patients had grade 1 tumor. Nine patients had recurrent meningiomas and four patients had newly diagnosed disease. Overall, the 68Ga-DOTATATE PET scan led to a change in the previously formulated treatment plans in 6 of 13 patients. Additionally, 8 of the 13 patients had foci of disease not appreciated on post-contrast MRI.

Conclusion: In this series, incorporation of 68Ga-DOTATATE PET imaging had clinical utility for most patients in whom it was used. It proved particularly useful in demonstrating intraosseous meningiomas, differentiating between recurrence and post-operative changes, and identifying sub-centimeter foci of disease. We recommend incorporating this imaging method as part of postoperative SRS for patients with meningiomas.


Michael SCHULDER (Lake Success, NY, USA)
15:40 - 15:50 #29904 - OP17 Growth dynamics of incidental meningiomas - A prospective long-term follow-up study.
OP17 Growth dynamics of incidental meningiomas - A prospective long-term follow-up study.

Background: There is no consensus for the management of incidental meningiomas. The literature on long-term growth dynamics is sparse and the natural history of these tumors

remains to be illuminated.

Methods: We prospectively assessed long-term tumor growth dynamics and survival rates during active monitoring of 62 patients (45 female, mean age 63.9) harbouring 68 tumors.

Clinical and radiological data was obtained every 6 months for two years, then annually.

Results: The natural history of incidental meningiomas during 12 years of monitoring was growth (p < 0.001). However, mean growth decelerated and became insignificant at 1.5 years.

Self-limiting growth patterns were seen in 43 (63.2 %) tumors, non-self-limiting in 20 (29.4%) and 5 (7.4 %) were indecisive due to ≤ 2 measurements. Decelerating growth persisted

once established. During follow-up, 38 (97.4 %) of 39 tumor treatments were initiated within 5 years. None developed symptoms prior to intervention. Tumor volume (p < 0.001) and relation to

venous sinuses (p = 0.039) correlated with more aggressive growth. Since inclusion 16 (25 %) patients died of unrelated causes and 2 (3 %) from atypical tumors.

Conclusion: Active monitoring seems an optimal first line management for incidental meningiomas. Intervention was avoided in > 40 % with indolent tumors. Nearly all treatments

were initiated within five years and were not compromised by tumor growth. Clinical follow-up seems sufficient beyond five years if self-limiting growth is established. Tumors with

steady or accelerating growth warrant monitoring until they reach a stable state or treatment is mandatory.


Torbjørn Austveg STRØMSNES (Bergen, Norway), Morten LUND-JOHANSEN, Geir Olve SKEIE, Geir Egil EIDE, Bente Sandvei SKEIE
15:50 - 16:00 #30046 - OP18 Assessment of post-radiosurgery response for intracranial meningiomas: is volumetric analysis the proper outlook?
OP18 Assessment of post-radiosurgery response for intracranial meningiomas: is volumetric analysis the proper outlook?

Defining both a threshold of progression and the optimal endpoint for clinical trials on radiation therapy for benign meningiomas is difficult. In fact, the growth rates of meningiomas are variable, overall survival (OS) is often very long, and progression-free survival (PFS) requires long-term follow-up. To assess radiation response various strategies have been evaluated. Although most of the published studies describe the criteria for control assessment, there is no uniform definition. Volumetric analysis of magnetic resonance imaging (MRI) imaging has been proposed as the most appropriate method for detecting change in slowly evolving brain tumors. In this scenario, we analyzed this method in post-radiosurgical intracranial meningiomas as part of a prospective clinical trial.

The primary aim of the present study was to validate a volumetric assessment method after fractionated radiosurgery or fractionated stereotactic radiotherapy (fSRS) for benign intracranial meningiomas. Secondary aims were evaluation of a cut-off to define progression, stable or partial response and volumetric response after fSRS treatment. To validate the volumetric assessment, we appraised delta values (ΔV) of volume variations. To evaluate tumor response, a volumetric analysis has been performed by means of co-registration of each follow-up MRI on baseline MRI and contouring of the lesion on each post-treatment exam.

Overall, 150 patients were considered eligible for the purpose of the volumetric analysis. After a mean follow-up of 60.5 months (SD 17.45, median 59, range 14–101 months) the median reduction in tumor volume was -21.26%, (range -82.26% to 91.36%) to reach a median final tumor of 8.65 cm3 (range 0.38 - 56.28 cm3) that differed significantly from baseline (p < 0.001). Among 150 irradiated meningiomas, 75 (50%) ultimately regressed, 67 (45%) remained stable, and 8 (5%) progressed. Baseline volumes were similar in each group (p = 0.092), and final volumes were significantly larger in tumors that progressed (p < 0.001) supporting the use of a ΔV of 20% as a cutoff for progression. The mean %ΔV became significantly different by 10 months, with continued diversion up to 36 months.

Our results suggest quantitative volumetric assessment of tumor response to fSRS may help clinicians to better understand early response profiles and provide a valuable tool for patient management following fSRS for meningiomas.


Valentina PINZI (Milan, Italy), Anna VIOLA, Irene TRAMACERE, Sara MORLINO, Elena DE MARTIN, Marcello MARCHETTI, Laura FARISELLI

15:00-16:00
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B17
ORAL PRESENTATIONS
Physics (2)

ORAL PRESENTATIONS
Physics (2)

Moderators: Alexandru DASU (Chief Medical Phyicist) (Uppsala, Sweden), Elena DE PONTI (Director) (Monza, Italy)
15:00 - 15:10 #30138 - OP19 - WITHDRAWN - Image-guided margin assessment to LINAC-based radiosurgery for single and multiple brain metastases based on post-treatment CBCT shifts.
OP19 - WITHDRAWN - Image-guided margin assessment to LINAC-based radiosurgery for single and multiple brain metastases based on post-treatment CBCT shifts.

Purpose/Objective(s): The goal of single isocenter LINAC-based stereotactic radiosurgery (SRS) using non-coplanar HyperArc™ (Varian) technique is high-precision treatment delivery for patients with brain metastases (BM) while sparing normal brain tissue to avoid complications such as radionecrosis.  LINAC-based SRS is desirable due to patient comfort and short treatment times. Planning target volume (PTV) margin is critical for targeting the gross tumor volume (GTV) and while avoiding geometric miss.  The caveat to adding PTV margin is potentially increasing the risk of radiation necrosis. Therefore, setting a proper PTV margin is crucial for SRS. The purpose of our study is to provide image-guided margin assessment based on post-treatment cone beam CT (CBCT) shifts and its dosimetric impact to target coverage for single and multiple BM patients.

Materials/Methods: 55 BM patients with total of 117 brain lesions, receiving SRS treatments were retrospectively evaluated. All patients were immobilized with the Encompass support device (Qfix) and planned with HyperArc technique. The plans consisted of 52 single, and 17 multiple BM (number of lesions ranging from 2 to 7) plans. All multiple BM targets were within 6 cm of the planning isocenter. In total, 120 single and 72 multiple BM fractions were evaluated based on post-treatment CBCTs. To evaluate target coverage loss due to intrafraction motion, MIM software was used. Shifts from post-treatment CBCTs were applied to the planning CT, and PTV/GTV dosimetric coverage was evaluated.

Results:  To evaluate target coverage loss due to intrafraction motion, 117 single BM were considered.  Of those, 25 (21%) patients had 0-1 mm margin and 92 (79%) patients had 2 mm PTV margin. The significant loss of the target coverage was observed in PTVs and GTVs in patients with 0-1 mm margin. The maximum target coverage losses were as high as 40% for PTV, and 28% for GTV with the mean target loss of 10.57±8.80% for PTVs, 6.51±8.16% for GTV. In comparison, plans with 2-mm margin showed maximum PTV target coverage loss of 16%, and mean of 4.14±3.34%. GTV losses in this group was maximum of 1% with mean value of 0.04±0.11%. For all multiple metastases BM patients, a 2-mm margin was used and no significant GTV coverage loss was noted.

Conclusions: This study demonstrates that a 2-mm margin is adequate for treating single isocenter single and multiple BM patients using LINAC-based radiosurgery based on post-treatment CBCT shifts analysis of the target coverage loss due to intrafraction motion


Tatsiana REYNOLDS (St Paul, USA), Mustafa OZER
15:10 - 15:20 #29791 - OP20 Dosimetric impact of setup errors in single-isocenter VMAT radiosurgery for multiple brain metastases.
OP20 Dosimetric impact of setup errors in single-isocenter VMAT radiosurgery for multiple brain metastases.

Purpose

In stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) of multiple brain metastases (BM) using single-isocenter volumetric arc therapy (VMAT), intra-fraction positioning errors may affect target coverage. This study aims to investigate geometric and dosimetric accuracy in such applications.

 

Material and Methods

Twenty-eight patients (79 BM) treated with single-isocenter coplanar FFF-VMAT technique were analyzed. PTV was defined by a 2 mm isotropic GTV expansion. Pre-treatment setup errors were evaluated with cone-beam CT (CBCT) and corrected with a robotic six degrees-of-freedom couch. Intra-fractional errors for each fraction were measured by post-treatment CBCT and applied to the planning CT. Plans involving translations and rotations (Fx-plan) were re-calculated with Monaco Monte Carlo TPS. Original and Fx-plans were compared in terms of dosimetric parameters, performing the Wilcoxon-Mann-Whitney test (alpha=0.05). The relationships of the BM volume, maximum dimension, distance-to-isocenter, and barycentre shift with the difference in target coverage between the two plans were investigated.

 

Results

The median post-treatment 3D error was 0.4 mm (0.1–1.5) and the median maximum rotational error was 0.3° (0.1–1.2). Consequently, the median BM barycentre shift between original and Fx-plans was 0.5 mm (0.1–2.7). The median GTV volume was 0.16 cc (0.01–3.91), while the PTV had a median volume of 0.72 cc (0.12–7.46). Median values of BM maximum dimension and distance-to-isocenter were 9.4 mm (2.9–24.0) and 5.11 cm (0.89–7.52), respectively. The GTV D95% was reduced by >4% in only 2 BM (1 patient), while in 61 lesions (17 patients) a loss of coverage below 1% in the Fx-plan was observed. The PTV D95% decreased by 1.4% on average, and a dose reduction >1% occurred in 31 PTVs (16 patients). The mean increase of brain V12Gy (SRS) and V20Gy (fSRS) observed in Fx-plans was 0.4% (-0.6–3.6). The dosimetric comparison did not result statistically significant (p>0.05). The difference in target coverage did not show a good correlation with BM volume, maximum dimension, and distance-to-isocenter, but an acceptable linear regression was found with the BM barycentre shift: R2=0.45 and R2=0.50 for GTV and PTV D95% variations, respectively.

 

Conclusion

Due to the optimal patient setup, as well as the full six degrees-of-freedom corrections, the safety PTV margin, and the fast beam delivery, the dosimetric effects of residual setup and patient motion errors for multiple metastases cases are negligible. These findings warrant a potential reduction in the PTV margin with this treatment technique.


Valeria FACCENDA, Valeria FACCENDA (Monza, Italy), Denis PANIZZA, Denis PANIZZA, Sara TRIVELLATO, Valerio PISONI, Paolo CARICATO, Paolo CARICATO, Raffaella LUCCHINI, Raffaella LUCCHINI, Stefano ARCANGELI, Stefano ARCANGELI, Elena DE PONTI, Elena DE PONTI
15:20 - 15:30 #29870 - OP21 Improved Small Field Dosimetry for Radiosurgery Planning through Optimized MLC Modeling.
OP21 Improved Small Field Dosimetry for Radiosurgery Planning through Optimized MLC Modeling.

Purpose: Optimized multi-leaf collimator (MLC) parameters are essential for accurate beam modeling in radiosurgery planning, particularly in plans that involve very small fields, fields with high modulation and/or heterogenous medium. In collaboration with Brainlab (Munich, Germany), we demonstrate how improved MLC modeling yields greater consistency between measured and calculated dose for the Pencil Beam (PB) and Monte Carlo (MC) models used in Elements (Brainlab, Germany).

Methods: MLC parameters that define the tongue and groove (TnG) effect and transmission through rounded leaf tips were determined from 32 asynchronous sweeping gap fields, comprised of 8 TnG ratios for four different leaf gaps (Hernandez, 2017). Measurements were performed with 6FFF on a HDMLC Truebeam (Varian, USA). Dose was measured in water using an Exradin A12 (Standard Imaging, USA) positioned at isocenter at a depth of 10 cm and an SSD of 90 cm. Brainlab’s analysis of our measured data yielded updated MLC parameters for both PB (Dynamic Leaf Shift (DLS) and TnG) and MC (Radiological Leaf Shift (RLS) and TnG) models. Validation of these models were performed using multiple plans, with differing complexities, optimized and calculated in each planning Element – Multiple Metastases, Cranial SRS and Spine SRS.  29 PB and MC plans were calculated using a 1 mm dose grid and 1% uncertainty (MC). Validations were performed with Gafchromic XD film (Ashland, USA) in multiple heterogeneous and homogenous phantoms, using ExacTrac (Brainlab, Germany) for positioning. FilmQAPro (Ashland, USA) was used to compare calculated and measured dose.

Results: For PB, DLS and TnG were changed from 0.12 mm and 0.49 mm to 0.18 mm and 0.32 mm, respectively. Based on our measurements, Brainlab modified their MC model (version 3.0) to allow adjustment of RLS and TnG, which was not configurable in earlier versions (2.5 or earlier). RLS and TnG were determined to be 0.25 mm and 0.7 mm, respectively. Excellent agreement between calculated and measured dose was observed for all plans. Average gamma score of >98% + 2% for PB and >98% + 1.8% for MC using 2%/1mm criteria. Plans calculated with MC 2.5 showed marked improvement in gamma scores when recalculated with MC 3.0, with up to a 68% higher gamma score (3%/1mm) for a highly complex plan.

Conclusion: Accurate modeling of MLC can be achieved using asynchronous sweeping gap measurements. Improved Elements' beam models are critical to achieving excellent agreement between measurement and calculation, even for very complex and/or small fields.


Lauren WEINSTEIN (South San Francisco, USA), Matthew SKINNER, Thorsten BSCHORR, Wolfgang ULLRICH
15:30 - 15:40 #29373 - OP22 Appliance of CBCT of Leksell Gamma Knife Icon for improving accuracy of stereotactic radiosurgery.
OP22 Appliance of CBCT of Leksell Gamma Knife Icon for improving accuracy of stereotactic radiosurgery.

The Leksell frame G is well-known fixation device for stereotactic radiosurgery. There is an opinion that accuracy of fiducial-based CT registration is better in comparison to MRI. Some centers use only MRI scans for stereotactic radiosurgery without any clinical issues. However, different models of MRI scanners and protocols have different level of geometrical distortion, so the accuracy of 1 mm is a worldwide acceptance. The novel model of gamma knife Icon has received a build-in cone-beam CT module with quality assurance tools. Gentle calibration of CBCT results in greater level of expected accuracy (less than 0.1 mm). The distortion of MRI can therefore be defined for each patient before the start of the treatment. The partial displacement of the frame and in opposite frame deformation due to overtightening the fixation screws in addition to imaging error, can lead to lost of accuracy during treatment. 

The purpose of the research is to assess geometrical deviation of the stereotactic space defined by MRI fiducials with the help of integrated CBCT module.

We have analyzed 3-Tesla MRI and CBCT mean and axis-depended differences obtained from 110 patients. Median X, Y and Z linear shift was 0.05 mm, -0.05 mm and 0,6 mm respectively. Median X, Y and Z axial shift was 0.72º, 0.01º and -0,11º respectively. Median maximal shift displacement was 1,09 mm. CBCT-based definition was needed in 80.9% cases. Acceptable shift was found in 19,1% cases. The reasons for a decision were loss of coverage (below 95%), excess of tolerated dose to critical structures or shift more than 0.5 mm for functional radiosurgery. In one case, there was a shift of posterior screw with maximal shot displacement of 4.54 mm.

Correlation analysis showed positive correlation between length of anterior post and X-shift (p=0.02), X-rotation (p=0.003), Y-rotation (p=0.001). Strong negative correlation was shown between Z-coordinate of posterior commissure and maximal shot shift (p=0.000006). We have found also positive correlations between mean MRI fiducial error and X-shift (p=0.04), maximal MRI fiducial error and Y-shift (p=0,04). The calculated shift did not significantly differ between groups with short (29%) or long (71%) posts of the frame.

As conclusion, the calculated deviation of stereotactic space can depend on a number of factors like configuration of frame and Z-coordinate of target. Appliance of CBCT can prevent partial displacement of the stereotactic frame, reduce the impact of MRI distortion and frame deformation on accuracy of treatment.


Viacheslav RAK, Greg KOYNASH (Moscow, Russia), Olga EVDOKIMOVA
15:40 - 15:50 #30095 - OP23 A novel methodology for dosimetry audits focused on intracranial stereotactic radiosurgery applications.
OP23 A novel methodology for dosimetry audits focused on intracranial stereotactic radiosurgery applications.

With contemporary SRS, the interlinked dosimetry- and geometry-related treatment parameters, require a high-degree of accuracy and precision. This translates into the need for reduced uncertainties at each step of this complex procedure. This work presents an innovative phantom-based audit methodology that, combining results from different dosimetry methods, evaluates all stages of the radiotherapy chain, serving as an ideal tool to promote best practice and assure high-quality treatments. 

The phantom used was a 3D-printed head phantom, accommodating inserts for film, OSL, and gel dosimeters, calibrated at an SSDL. The user received an explicit, for the practice to be audited, RTstructure set, and was challenged to achieve a specific level of accuracy. Following the patient SRS treatment local protocol, the phantom treatment was simulated, planned, and exported to the delivery platform by the staff members who are normally involved at each step of the treatment chain. To assess whether QA results met the pre-defined standards, the latest recommendations of AAPM-RSS Medical Physics Practice Guideline 9.a. for SRS-SBRT were adopted for film dosimetry. A linac-based single-isocenter multi-focal SRS treatment was evaluated. 3 similar VMAT plans were generated, one for each detector type, taking into account the calibration dose range of each detector. Localization was performed with a kV CBCT. 6D corrections were applied prior to delivery. The OSL and film dosimeters were unloaded for analysis, and the phantom incorporating the irradiated gel-filled cylinder was MR scanned for the dose read-out 24 hours post-irradiation at a fully characterized MR scanner.

Results from one selected center audited has not indicated any concerns regarding the local practices for the specific aspects of dosimetry for intracranial SRS. Measured and calculated dose distributions were spatially co-registered and compared. Calculations were experimentally validated within uncertainties. The maximum deviation between measurements and TPS calculations for OSL dosimetry was 4.08%. The 3D GI of the film plane was 99.17% and the total spatial offsets of the planned and the corresponding gel-measured distributions for the targets involved were 0.77mm, 0.45mm and 0.81mm, respectively. Further work is required for the full characterization of OSLDs response to reduce the experimental uncertainties.

Novel dosimetry audit techniques allow the multi-step evaluation of the radiotherapy treatment chain. To keep up with the clinical need and novel equipment future developments will be focused on aspects such as treatment planning based on MR images and online intrafraction replanning strategies, as these are being increasingly applied into routine clinical services.


Kyveli ZOURARI, Emmanouil ZOROS, Georgios KALAITZAKIS, Themistoklis BOURSIANIS, Thomas MARIS, Evangelos PAPPAS (ATHENS, Greece)
15:50 - 16:00 #29878 - OP24 Iba myqa srs detector for cyberknife radiosurgery quality assurance.
OP24 Iba myqa srs detector for cyberknife radiosurgery quality assurance.

Background and Aims

Dose administration accuracy in radiosurgery (RS) treatments is of paramount importance to guarantee both the clinical outcome and the absence of severe toxicities. A comprehensive delivery quality assurance (DQA) program is therefore mandatory. In this study we evaluated the IBA myQA SRS® (IBA Dosimetry, Germany) high-resolution solid-state detector in a new context of RS delivered using CyberKnife® (Accuray, US) 6 MV robotic linac. The detector’s performance was investigated in periodic machine DQA and patient-specific treatments verification.

 

Methods

MyQA SRS [Figure 1] is composed of a 140×120 mm CMOS matrix with 400 um resolution, allocated in a cylindrical ABS phantom topped by a hemispheric cap. Dose calibration was ensured delivering 500 cGy to the matrix central area by an ad-hoc optimized plan.

System performance evaluation included: periodic dosimetry tests (dose linearity and reproducibility, output factors, off-axis-ratios) [Figure 2], detector angular response and dose rate dependence (in the clinically useful source-to-surface range between 650 mm and 1200 mm), and variable aperture IRIS® collimator field size measurement.

For patient-specific DQA, the system performance was studied for various RS intracranial targets considering complete optimized plans and plans corrected taking into account the device angular response (delivered after removal of beams above a threshold angle selected according to the angular dependence analysis). An evaluation by 3% 1 mm Gamma Index was performed [Figure 3].

 

Results

Detector response for periodic DQA tests was always found to be in accordance with the authors center’s   commissioning data. Dependence from dose rate was confirmed, corroborating the manufacturer requirement of a dose calibration specific for each dose rate of interest. Field dimensions for the IRIS collimator were consistent with commissioning values, with an accordance within 0.4 mm. Finally, angular dependence tests resulted in a signal decay greater than 5% when beams outside a ±50° amplitude cone with respect to the patient’s anterior-posterior direction were delivered.

Concerning patient-specific QA, >50° angled beams elimination from treatment delivery led to an improvement in Gamma Index passing rates ranging between +3% and +115%, depending on target and plan characteristics. 

               

Conclusions

IBA myQA SRS proved to be a suitable device for constancy and daily DQA, providing high-resolution real-time results and showing a potential for replacing radiochromic films in many dosimetric analyses. Preliminary patient-specific QA Gamma tests showed high passing rates once angular dependence corrections were performed, even when high complexity treatments, such as the trigeminal neuralgia case, were considered.


Francesco PADELLI (Milano, Italy), Domenico AQUINO, Laura FARISELLI, Elena DE MARTIN

15:00-16:00
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C17
3D Skull-base Anatomy for Safe Radiosurgery (2)

3D Skull-base Anatomy for Safe Radiosurgery (2)

Coordinator: Siviero AGAZZI (Tampa Florida, USA)
Keynote Speaker: Siviero AGAZZI (Tampa Florida, USA)

16:00 - 16:30 COFFEE BREAK AND EXHIBITION
16:30
16:30-17:30
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A19
ORAL PRESENTATION
Other Benign Brain Tumors, Pediatric SRS, Ocular Disorders

ORAL PRESENTATION
Other Benign Brain Tumors, Pediatric SRS, Ocular Disorders

Moderators: Isa BOSSI ZANETTI (Radiation Oncologist) (Milano, Italy), Antonio DE SALLES (Professor - Chief) (SÃO PAULO, Brazil)
16:30 - 16:40 #29449 - OP25 Stereotactic Radiosurgery for Rathke’s Cleft Cysts: An International Multicenter Study.
OP25 Stereotactic Radiosurgery for Rathke’s Cleft Cysts: An International Multicenter Study.

Objective: Rathke’s cleft cysts (RCC) are sellar collections from an incompletely regressed Rathke’s pouch. Common symptoms can include headaches, visual loss, and endocrinopathy. In some cases of symptomatic or growing RCC, surgery is required. Recurrence after surgery is common (10-40%). Stereotactic radiosurgery (SRS) has been used in an attempt to control growth and symptoms, but outcomes are not well known. We sought to study the outcomes of Rathke’s cleft cysts following Gamma Knife radiosurgery for both salvage and initial treatment.

Methods: We reviewed the outcomes of 25 Rathke’s cleft cyst patients that had stereotactic radiosurgery between 2001 and 2020. Four patients received upfront SRS, and 21 were treated with salvage SRS. Diagnosis was based on imaging or histopathology. Cyst control was defined as stability or regression of the cyst. Kaplan-Meier analysis was used to determine time-to-recurrence and determine potential factors for recurrence.

Results: The respective median clinical follow-up and margin dose were 6.5 years and 12 Gy. Overall control was achieved in 19/25 (76%) patients, and four recurrences required further intervention. For those that recurred, the average time to recurrence was 35.6 months. Visual recovery occurred in 14/15 (93.3%) patients, and no new post-radiosurgery visual deficits occurred. The presence of pre-treatment visual deficit was often an indicator of regrowth. 3 of 3 patients with hyperprolactinemia resolved after SRS. New endocrinopathy related to radiosurgery was noted in 5/25 (20%) patients, all of which were thyroid and/or cortisol axis related. Upfront SRS was used in four patients. No new endocrinopathies or visual deficits developed after upfront SRS, and the single patient with a pretreatment visual deficit recovered. One of the four upfront SRS patients recurred, after 7.5 years.

Conclusion: Stereotactic radiosurgery produced effective recovery of visual deficits, and carries a low risk for new visual deficits. Cyst control was achieved in about three quarters of the patients. Following radiosurgery, patients without pre-treatment visual deficits are less likely to regrow. Endocrinopathy can occur after radiosurgery, similar to other sellar mass lesions. Initial radiosurgery shows the potential for long-term cyst control, with improvement of symptoms and low risk for complications.


Douglas KONDZIOLKA (New York, USA), Roberto MARTINEZ-ALVAREZ, N MARTINEZ-MORENO, Joshua SILVERMAN, Kenneth BERNSTEIN, Jason SHEEHAN, Roman LISCAK, Jaromir HANUSKA, Huai-Che YANG, Cheng-Chia LEE
16:40 - 16:50 #30239 - OP26 Clinical analysis of gamma knife radiosurgery in the treatment of trigeminal schwannomas: 26-years’ experience of a single institution.
OP26 Clinical analysis of gamma knife radiosurgery in the treatment of trigeminal schwannomas: 26-years’ experience of a single institution.

We aimed to evaluate the radiographic and clinical outcomes after gamma knife radiosurgery (GKRS) for trigeminal schwannomas (TSs). A total of 87 patients who underwent GKRS for TSs between 1991 and 2020 were enrolled. The mean tumor volume was 4.3 cm3. The median prescribed dose for the margins of the tumor was 13 Gy. The median follow-up duration was 284.6 months (range 12.0–311.5 months). The overall local tumor control rate was 90%, and the symptom response rate was 93%. The response rate for each symptom was 88% for facial pain, 97% for facial sensory change, and 86% for cranial nerve deficits. Fifteen (21%) patients showed transient swelling, which had regressed at the time of the last follow-up. Cystic tumors were associated with transient swelling (p = 0.04). A tumor volume of < 2.7 cm3 was associated with local tumor control in univariable analysis. Transient swelling was associated with symptom control failure in both univariable and multivariable analyses (p = 0.04, odds ratio 14.538). GKRS is an effective treatment for TSs, both for local control and symptom control. Transient swelling and tumor progression were associated with symptom control failure. Tumor volume < 2.7 cm3 was associated with local control.


Dong-Won SHIN, Young-Hoon KIM (Seoul, Korea), Sang Woo SONG, Young Hyun CHO, Chang-Ki HONG, Jeong Hoon KIM
16:50 - 17:00 #29908 - OP27 Long term Outcomes after Gamma Knife Stereotactic Radiosurgery for Glomus Jugulare tumors. Analysis of 47 patients.
OP27 Long term Outcomes after Gamma Knife Stereotactic Radiosurgery for Glomus Jugulare tumors. Analysis of 47 patients.

Introduction

Glomus jugulare tumors are benign but locally destructive lesions located in one of the most poorly accessible regions of skull base. Excision is potentially curable but is fraught with risk of injury to the surrounding neurovascular structures. Even with preoperative embolisation bleeding during operative removal may be excessive.

The aim of the present study was to ascertain the long term safety and efficacy of Gamma Knife Radiosurgery as primary or adjunctive form of therapy.

Methods

From May 2008 till December 2020, 3525 patients underwent radiosurgery with Leksell Gamma Knife unit (Model C) and ICON at Pakistan Gamma Knife Center. Forty seven patients had glomus jugulare tumor. A retrospective analysis of treatment results was performed. There were 26 female and 21 male patients. The age of the patients ranged from 20 to 70 yrs.(Mean 42.8 yrs.). Two pts. had undergone microsurgery with incomplete resection. None of the patient had previous radiotherapy or undergone embolisation.

A median tumor volume 13.49 cm3 ,(range 466.7mm3 to 27.5cm3) was covered by median isodose volumes of 45%(range 43-50%). A median isodose of 14 Gy (range 12 to 16 Gy) was applied to the tumor margin. The median no. of isocenters was 18 (range 2-28).Treatment planning was conducted using MR imaging along with CT scanning in all cases. The mean coverage of the tumor with the prescribed minimal radiation dose was 95.2% (range 82 to 99%).

Results

Thirty two patients had a follow up of at least six months with a median interval of 60 months following GKS (range 6-144 months). Neurological follow up examinations revealed improved clinical condition in 24 patients (75%),a stable neurological status in 6 patients (19%), and progression in symptoms in two patient(6%). Follow up MR imaging was conducted in 24 patients. Tumor size has decreased in 15 patients (66%) and the volume remained unchanged in the seven (28%). Two of the tumors showed volumetric increase during the observation period for which repeat gamma knife radiosurgery was done.

Conclusions

Our long term results show that gamma knife radiosurgery is a safe and efficacious treatment option for primary or residual glomus jugulare tumors with no significant morbidity.

Gamma knife radiosurgery can be used as an upfront treatment of glomus jugulare tumors.

 

 

Correspondence:

Dr M Abid Saleem

 Consultant Neurosurgeon,Gamma Knife Radiosurgery Center. Dow University of Health Sciences.Ojha campus.Karachi

Email.abid.saleem@duhs.edu.pk

Cell:00923323414304.


M Abid SALEEM (Karachi, Pakistan), Atif MANSHA, Amjad SHAHANI, Sohail HUSSAIN
17:00 - 17:10 #29420 - OP28 Hypofractionated Stereotactic Radiosurgery for Craniopharyngioma.
OP28 Hypofractionated Stereotactic Radiosurgery for Craniopharyngioma.

Objectives: Craniopharyngiomas are benign tumors arising from embryonic remnants of the Rathke’s pouch and often present with visual impairment and hypopituitarism. Although surgery with gross total resection is considered the treatment of choice, it is mostly not feasible due to proximity to critical structures such as the optic nerve and hypothalamic-pituitary axis. Gamma Knife radiosurgery (GKRS) has been reported as a reasonably safe and effective management option in selected craniopharyngioma patients; however, there is no data regarding hypofractionated GKRS (hf-GKRS) in these patient group. This retrospective, single-center study evaluated patient outcomes of hf-GKRS for craniopharyngioma.

Methods: Twenty-two patients with histologically verified craniopharyngiomas were treated with hf-GKRS. The mean age of the patients was 36 years (range, 3-66 years). Prior to hf-GKRS, the vast majority (82%) of patients presented with visual deficits and panhypopituitarism was detected in 6 patients (27.3%). Cystic morphology was observed in 12 lesions (54.5%). Fifteen patients (71%) received single surgical resection and 6 patients (29%) underwent multiple surgeries. One patient was diagnosed with biopsy. The mean tumor volume was 2.3 cm3, ranging between 0.2-7.8 cm3The most commonly used fractionation scheme was 5x4 Gy (82%).

Results: The mean follow-up was 21.7 months (range, 14-35 months). Local tumor control was achieved in 17 patients (77.3%), with 10 tumors (22.7%) decreased in size and 7 (31.8%) remained stable. Local tumor control rates showed a wide variety among lesions of different morphologies; 100% in solid lesions, 91.7% in cystic, and 33.3%in mixed lesions (p<0.05). Visual, endocrinological, and clinical status were stable in 18 (81.8%) and worsened in four (18.2%) patients. No adverse radiation effects were observed. Only 13.5% of patients underwent additional treatments, represented by additional surgical resection in two patients (9.1%) and repeat hf-GKRS in one patient (4.6%).

Conclusions: To the best of our knowledge, this is the largest single-center study that addressed the outcomes of hf-GKRS utilized in the management of post-operative craniopharyngiomas. A high tumor control rate was achieved over sufficient follow-up, which demonstrates the efficacy and safety of hypofractionation in both prevention of tumor growth and additional risks of alternative treatments. Further, well-designed studies are required to establish the long-term efficiency of hf-GKRS in the management of craniopharyngiomas. 


Yavuz SAMANCI (Istanbul, Turkey), Muhammed Amir ESSIBAYI, Mustafa BUDAK, Fatih KARAKÖSE, Selçuk PEKER
17:10 - 17:20 #29408 - OP29 Demographic of Gamma Knife Radiosurgery in pediatric patients.
OP29 Demographic of Gamma Knife Radiosurgery in pediatric patients.

Objective

 

Although radiation modalities are common among pediatric patients, GKRS is a rare modality. The objective is to show the patient demographic in a reference GKRS service over 20 years and different applicability.

 

Method:

 

Retrospective review of patients under 18 years treated with GKRS from 1999 to 2020. It was considered the primary pathology, age, dose, lesion volume, use of frame versus mask, single session versus hypofractionation. Gamma Knife Model C, Perfection and Icon were used.

 

Results

 

Fifty-five patients were submitted to 80 treatments, age varied from 3 to 18, being the majority between 15 and 18 yo. Tumors represented 55% and AVMs 45%. Seventy-three procedures used Leksell frame and 7 used thermoplastic mask, being 6 for single session and 1 for 5-session hypofractionation for chiasm protection. Median dose was 20Gy (8-28) and lesion volume was 1.066cc (0.081-34.791). Eloquent area and brain stem lesions were safely treated with good response

 

Conclusion

GKRS is a visible modality for radiation treatment for pediatric patients allowing several techniques for a great variety of pathologies. For younger patients, sedation is needed for tolerance and safety. GKRS is an applicable treatment modality for pediatric patients and individual considerations with a multi-disciplinary team should be made.


Victor GOULENKO, Dheerendra PRASAD (Buffalo, NY, USA)
17:20 - 17:30 #30026 - OP30 Single fraction radiosurgery as an eye salvage treatment of children with resistant or recurrent intraocular retinoblastoma.
OP30 Single fraction radiosurgery as an eye salvage treatment of children with resistant or recurrent intraocular retinoblastoma.

Background: Conventional external beam radiotherapy is currently in use only as a second-line (salvage) therapy of intraocular retinoblastoma (Rb) because of serious complications including secondary malignant tumours in the field of irradiation. There is no data of using stereotactic radiosurgery (SRS) in Rb treatment.

The aim of the study is to present 6-year experience of using SRS in children with intraocular Rb.

Materials and methods: Nineteen children (20 eyes) were treated using SRS in the period from 2015 to 2021. Seventeen eyes were treated with GammaKnife SRS, 3 with Cyber-knife SRS. Mean patient age was 34.4 months (range, 12-114 months). The eyes were classified as group B (n=4), C (n=1), D (n=14), E (n=1). Four children had the only eye. All patients were pretreated with systemic and local chemotherapy and all types of focal treatment before using SRS. Recurrent and resistant Rb with parent’s refusal to remove the eye was the indication for SRS. There was mean dose 21.8 Gу (range, 20-24) with marginal 50% isodose for GammaKnife SRS and mean dose 31.5 Gу (range, 27.5-35) with prescribed dose 26.8 Gy (range, 24-28.5) and mean 75% Isodose for Cyber-knife treatment, depending on tumour type and location. Radiation doses were evaluated accounting critical eye structures and the orbit bones. Three types of target planning were evaluated according to Rb location and extension.

Results: Complete tumour regression was achieved in 15 patients, partial in 3. Fifteen eyes (75%) were salvaged. Two eyes were enucleated because of tumour growth, 3 eyes because of severe complications - vitreous hemorrhage with total retinal detachment. Hemorrhagic complications of different severity occurred in 50% of patients within the period from 1.5 to 58 months (mean, 8.6) as a late sign of vascular radiation damage. It was treated using both intraocular surgery or medication. Cataract occurred in 3 patients and was removed successfully. There were no acute complications, no cases of keratopathy or damage of orbital tissues. Mean follow-up 39.4 months (range, 3-74 months).

Conclusion: SRS as an alternative to enucleation in patients with Rb was proved to be a reasonable option to save the eye despite the high amount of vascular complications. Differences between GammaKnife and Cyber-knife SRS should be analyzed. Outcomes within the longer follow up is essential.

Andrey YAROVOY (Moscow, Russia), Andrey GOLANOV, Vera YAROVAYA, Valery KOSTJUCHENKO, Natalya ANTIPINA, Arina LESTROVAYA

16:30-17:30
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B19
ORAL PRESENTATION
Brain Metastases (1)

ORAL PRESENTATION
Brain Metastases (1)

Moderators: Hyun-Tai CHUNG (Professor) (Seoul, Korea), Antonio SANTACROCE (neurosurgeon radiation oncologist) (Munich, Germany)
16:30 - 16:40 #29809 - OP37 Significant Survival Improvements for Patients with Melanoma Brain Metastases: Can We Reach Cure in the Current Era?
OP37 Significant Survival Improvements for Patients with Melanoma Brain Metastases: Can We Reach Cure in the Current Era?

Objective

New therapeutic options for both brain metastases (BM) and extracranial melanoma care have been associated with increasing survival expectations. Ten years ago, median survivals after the diagnosis of a melanoma brain metastasis were in the range of 5 to 7 months. Using a prospective registry, our aim was to define current survival goals for melanoma patients with brain metastases, based on state-of-the-art multimodality care.

Methods

We reviewed 171 consecutive melanoma patients with brain metastases receiving stereotactic radiosurgery (SRS) who were followed with point-of-care data collection between 2012-2020. Demographic, clinical, histological and imaging data were collected, including systemic treatment, radiosurgical parameters and outcomes.  We evaluated factors predicting survival and tumor control, including survival without any need for systemic or local therapy.   

Results

The mean patient age was 65 years (20-91), 39% were female and 29% had BRAF-mutated tumors. The median overall survival after radiosurgery was 15.7 months (95% Confidence Interval [CI]: 11.4-27.7 months). We identified 32 patients who had survival of at least 5 years from an initial brain tumor radiosurgery.

Patients on immunotherapy had a significantly longer survival in comparison to the rest of the population (p=0.012). BRAF mutations did not show a significant influence on survival in comparison to the wild type (p=0.2) and use of targeted therapies showed survival advantage in comparison to chemotherapy (p=0.009), but not to immunotherapy (p=0.09).  In a multivariate analysis, both immunotherapy and the number of metastases treated at the first SRS were significant predictors of long-term survival of over 5 years from initial SRS (p=0.023 and p=0.018, respectively). Five patients (16%) of the long-term survivors’ cohort required no active treatment for more than 5 years.

 

Conclusions

Long-term survival in patients with melanoma brain metastases is achievable in the current era of stereotactic radiosurgery combined with systemic immunotherapies. For those patients alive more than 5 years after first SRS for brain metastases, 16% had been also off systemic or local brain therapy for over 5 years. Given late recurrences of melanoma, caution is warranted, however prolonged survival off active treatment in a small subset of our patients raises the potential for cure.


Assaf BERGER (New York, USA), Kenneth BERNSTEIN, Juan Diego ALZATE, Reed MULLEN, Joshua.s SILVERMAN, Erik SULMAN, Bernadine R. DONAHUE, Anna C. PAVLICK, Jason GUREWITZ, Monica MUREB, Janice MEHNERT, Kathleen MADDEN, Amy PALERMO, Jeffrey S. WEBER, John G. GOLFINOS, Douglas KONDZIOLKA
16:40 - 16:50 #30082 - OP38 Risk of symptomatic intracranial hemorrhage exceeds the risk of radiation necrosis in patients with melanoma brain metastases following definitive SRS treatment.
OP38 Risk of symptomatic intracranial hemorrhage exceeds the risk of radiation necrosis in patients with melanoma brain metastases following definitive SRS treatment.

Background: Melanoma brain metastases (MBM) are prone to hemorrhage. It is unclear how that risk of bleeding is influenced by treatment with SRS with or without concurrent immunotherapy (IO) compared to the risk of radiation necrosis (RN).

 

Methods: We performed a retrospective study of 182 melanoma patients treated at a single institution with at least one course of SRS. We captured several covariates including the type and timing of brain radiotherapy and concurrent systemic treatment (BRAF-targeted therapy, IO, chemotherapy, or none). Toxicity was graded using the Common Terminology Criteria for Adverse Events v5.0 criteria. Cumulative incidence (CI) of post-SRS hemorrhage and RN were estimated using models with death and WBRT as competing risks. Secondary endpoints included: local failure (LF), distant brain failure (DBF), time to post-SRS brain surgery, and overall survival (OS).

 

Results: A total of 595 MBM were treated with definitive SRS. CI of grade 2+ post-SRS hemorrhage at 12 months was 24%, in the absence of any systemic treatment, 13% in patients who received BRAF-targeted therapy (HR 0.49 [0.13-1.78], p=0.28), and 7% in patients who received IO (HR 0.27 [0.13-0.71], p=0.0071). CI of grade 2+ RN 12 months after SRS was 4%, 5%, and 3% with dual agent IO, single agent IO, and no IO, respectively (NS). Lesion size correlated to the risk of symptomatic RN (HR 1.1, p<0.001) but not post-SRS hemorrhage. Similarly, prescription dose correlated to the risk of grade 2+ RN (HR 37.84, p<0.001) but not hemorrhage. CI of LF at 24 months was 5% with no IO, 3% with dual agent, 2% with Ipilimumab (HR 0.71, p=0.67), 11% with Pembrolizumab (HR 4.3, p=0.031) and 18% with Nivolumab (HR 4.27, p=0.052). CI of DBF was similar in patients who did or did not receive IO (~70%).

 

Conclusions: Following SRS for MBM, the risk of symptomatic RN with or without IO was low, whereas the risk of hemorrhage was considerable, but significantly decreased with concurrent IO administration. We hypothesize that intracranial bleeding is the predominant risk in MBM patients following SRS and is reduced by concurrent administration of IO. Future efforts will include studying the risk of bleeding with IO alone as well as the mechanisms by which IO might decrease the risk of intracranial hemorrhage.


Paola Anna JABLONSKA (Toronto, Canada), Jessica WEISS, Amy Liu ZHIHUI, Paul KONGKHAM, Marcus BUTLER, David B. SHULTZ
16:50 - 17:00 #30142 - OP39 Low-dose radiosurgery for brain metastases: can acceptable local control be achieved?
OP39 Low-dose radiosurgery for brain metastases: can acceptable local control be achieved?

 

 

Objectives:

Dose selection for SRS classically has been based on tumor diameter with reduction of dose in the settings of prior brain irradiation, larger volumes, eloquent location, and larger number of metastases. RTOG recommended a dose of 15 Gy for lesions >3 cm in diameter, however, retrospective series have shown local control rates to be potentially as low as 50% for larger lesions. However, the literature has not been consistent when exploring low-dose response. The aim of this study is to report the local control (LC) and toxicity when low-dose SRS is used to treat BM and to explore for predictors of these outcomes.

 

Methods:

A single institution, IRB-approved retrospective analysis was conducted of our prospective Gamma Knife (GK) SRS registry to identify patients with BM treated with low-dose, defined as margin dose ≤ 14Gy, from 2014 to 2020. Of the 107 patients with BM treated during this time, we identified 65 patients with 350 BM. Patient, tumor, and treatment characteristics were identified, and LC and toxicity was correlated to demographic, clinical, and dosimetric data.

 

Results:

Mean patient age was 58.3ys (21-82); histology of the primary was lung in 31, breast in 19, melanoma in 5, gastrointestinal in 4, renal cell carcinoma in 3, prostate in 2, ovary in 1 patient.  Median tumor volume was 0.93cc IQR (0.21-0.59), and mean margin dose was 13.1Gy (8-14). At a mean follow-up of 11.6 months (6-58), local failure (LF) was detected in 41/350 (11%). Actuarial LC at 1 year and at 18 months were 91.2% and 83% respectively. On univariate analysis, maximum dose ≤ 18.5Gy and mean dose ≤ 17Gy were significant predictors for LF (p=.024, p=.029). On multivariate analysis mean dose, volume and previous SRS was significant. Adverse radiation effects (AREs) were diagnosed in 4 (1.1%) patients, all of whom had received prior WBRT (p=0.005).

 

Conclusions:

It is feasible to achieve acceptable local control in BMs with low-dose SRS. Mean dose, maxim dose, and volume appear to be predictors for LF, and AREs are associated with previous WBRT. The value of low dose radiosurgery may be in the palliative management of patients with higher numbers of small tumors with the aim of brain tumor control and preservation of neurological function for as long as possible.

 

 


Juan Diego ALZATE (Cleveland, USA), Assaf BERGER, Kenneth BERNSTEIN, Joshua SILVERMAN, Tanxia QU, Bernadine DONAHUE, Douglas KONDZIOLKA
17:00 - 17:10 #29867 - OP40 Gamma knife radiosurgery for cystic brain metastases: Institutional experience.
OP40 Gamma knife radiosurgery for cystic brain metastases: Institutional experience.

Introduction:

Gamma-Knife radiosurgery (GKRS) is a well-established treatment for brain metastases (BM). The imaging features of BM can variably have either homogeneous and heterogenous enhancement, or cystic-like appearances. These features can represent different biological behaviors concerning the treatment of these lesions. Cystic BM (cBM) are perceived to be more resistant to treatment than solid BM (sBM). In this study, we sought to compare the response rates and overall survival of patients with cBM relative to sBM after GKRS.

Method:

Patients treated for BM with GKRS over a 2-year interval (2016-2017) were evaluated. GKRS dosing was delivered per RTOG 90-05 according to our standard protocol. Patients were divided in 3 groups: those with cBM only, sBM only, and both cystic and solid BM (csBM). Kaplan-Meier analysis with the log-rank test was used to calculate and compare overall survival (OS) between groups. Local control was analyzed utilizing RECIST criteria at 3, 6, and 12 months. Chi-square analysis compared the response rate for cBM and sBM.

Result:

73 patients (59% female) with a mean age 67 years (range: 43-91) were analyzed. The most frequent pathologies were lung (54%) and breast (18%). KPS was ≥70 in 66 patients (90%). Prior to GKRS treatment, 22% of patients received WBRT, 71% chemotherapy, 22% had prior surgery, and 16% received immunotherapy. No significant differences were found in the clinical characteristics between patient groups. Mean OS was 20 months (2-38, 95% CI) for the cBM patient group, 17 months (12-22, 95% CI) for sBM patient group and 13 months (7-19, 95% CI) for csBM patient group (p = .967). Of the 416 lesions evaluated, 15% (n=62) were cBM and 85% (n=354) were sBM.cBM were significantly larger than sBM (p < 0.0001) and therefore cBM received significantly lower doses of radiation (p 0.001). No other significant differences were found between cBM and sBM. Local control at 6 months was 92% for cBM and 89% for sBMs (p =.49).

Conclusion:

Despite a perceived worse prognosis, our results suggest that patients harboring cBM treated with GKRS achieve similar oncologic outcomes when compared with patients with sBM. cBM are usually larger than sBM and therefore these lesions may be treated with less radiation dose than their solid counterparts. Regardless, cBM and sBM are suitable stereotactic radiosurgery targets with comparable local control rates.


Lilyana ANGELOV (Cleveland, USA), Josue AVECILLAS CHASIN, Auston WEI WEI, Yusuke HORI, Sam CHAO, Alireza MOHAMMADI, Glen STEVENS, John SUH, Gene BARNETT
17:10 - 17:20 #29985 - OP41 Stereotactic radiosurgery for bladder cancer brain metastases: International Radiosurgery Research Foundation (IRRF) multicenter study.
OP41 Stereotactic radiosurgery for bladder cancer brain metastases: International Radiosurgery Research Foundation (IRRF) multicenter study.

Introduction. Bladder cancer only rarely metastasizes to the brain. As such, the optimal management strategy is not well defined. This study was performed to evaluate the results of SRS as part of the management of bladder cancer brain metastases.

Methods. Centers participating in the IRRF were asked to review their database to identify bladder cancer patients who had SRS for related brain metastases and at least one clinical or imaging follow-up. Outcomes included post-SRS overall survival, local and distant control and clinical evolution.

Results. 103 patients from 10 institutions met inclusion criteria and received SRS for a total of 301 brain metastases. Median age at SRS was 68 (range, 31-84) and 73.8% of patients were male. Median KPS was 80% (range, 50-100%). Median time from primary to brain metastases diagnosis was 18 months. At the time of SRS, 50% of patients had active non-CNS disease. Prior management of brain disease included surgical resection in 28.4% and WBRT in 4.9% of patients. At SRS, the median number of metastases treated per patient was 1 (range, 1-22), and median cumulative SRS volume was 1.16 cc (range, 0.01-44 cc). Most patients had single fraction SRS using a median margin dose of 18 Gy (range, 12-33 Gy). At the time of analysis, 9.7% of patients were still alive. The median overall survival after SRS was 7 months. Actuarial survival was 58.8%, 36.9% and 17.0% at 6, 12 and 24 months, respectively. Local control as defined by RANO criteria was achieved in 89.3% of metastases. Actuarial local control of treated metastases was 88.3% at 12 months and 74.2% at 24 months. During follow-up, 42% of patients developed new remote brain metastases and 4.9% had leptomeningeal dissemination. Subsequent management of uncontrolled brain metastases included repeat SRS in 21.7%, surgical resection in 8.8% and WBRT in 7.6% of patients. At last follow-up, 32.1% of patients had improvement of their neurological condition, whereas 38.5% remained stable. Steroids were discontinued in 50.9% of patients. Radiation necrosis was seen in 4.3% of treated metastases. On multivariate Cox regression analyses, female sex and better KPS were predictors of improved survival. For local control, lower SRS volume, absence of corticosteroid intake and adjuvant chemotherapy were predictors of better tumor control.

Conclusion. SRS is a safe and effective management option for the management of brain metastases in bladder cancer patients.


Rémi PERRON, Christian IORIO-MORIN, Tomas CHYTKA, Gabriela SIMONOVA, Veronica CHIANG, Charu SINGH, Ajay NIRANJAN, Zishuo WEI, L.dade LUNSFORD, Selcuk PEKER, Yavuz SAMANCI, Jennifer PETERSON, Richard ROSS, Chad RUSTHOVEN, Cheng-Chia LEE, Huai-Che YANG, Ulas YENER, Jason SHEEHAN, Douglas KONDZIOLKA, David MATHIEU (Sherbrooke, Canada)
17:20 - 17:30 #29907 - OP42 Treatment of multiple metastases and high volume disease with stereotactic radiosurgery: a single centre experience.
OP42 Treatment of multiple metastases and high volume disease with stereotactic radiosurgery: a single centre experience.

Background:

Stereotactic radiotherapy for patients with 10 or more brain metastases is controversial. Difficulties with planning, treatment times and concerns about survival lead to whole-brain radiotherapy for many. High-volume intracranial disease (≥10cc) has also been shown to correlate with poor survival. However, prospective, randomised data is lacking.

 

Methods:

A radiosurgical-board approved, retrospective cohort study was performed. 353 patients treated for metastatic brain disease at a single Gamma Knife centre from Jan-2010 to Aug-2021 were analysed. Data was censored from January 2022. A Kaplan-Meier analysis was performed to determine survival post-stereotactic radiosurgery of patients with 10 or more metastases against a matched group of 5-9 metastases and 1-4 metastases. A further Kaplan-Meier analysis was performed of patients with 10cc or more intracranial metastatic disease treated against a matched group of less than 10cc. A logrank test assessed for statistical differences in survival. A multivariate Cox regression was performed to assess the relationship between overall survival and: number of metastases; total volume; primary malignancy; the use of systemic anti-cancer therapies with intracranial penetrance; and whether there was controlled extracranial disease. Data was checked for multicollinearity with the Belsley-Kuh-Welsch technique and for proportional hazards according to Schoenfeld residuals. Results with p-values <0.05 were considered significant.

 

Results:

Survival data was available for all 353 patients, and for 85-100% of patients for factors analysed in multivariate analysis. The minimum follow-up period was 5 months. 63 patients with ≥10 metastases (median 19 metastases) were identified. Median survival measured 13.3 months, compared with 15.1 months for the 5-9 metastasis group and 19.0 months for the 1-4 metastases group. Differences in survival did not reach statistical significance (p-value 0.14). 85 patients with ≥10cc total intracranial disease (median 14.85cc) were identified. Median survival for the ≥10cc group measured 17 months compared with 18.5 months in the <10cc group. Differences in survival reached statistical significance (p-value <0.01). Increasing total volume of disease (HR 1.05 [1.01-1.09], p-value: 0.01), non-small cell lung cancer primaries (HR 3.5 [1.35-9.09] p-value: 0.01) and the use of systemic anti-cancer therapy with intracranial penetrance (HR 0.239 [0.105-0.547] p-value: <0.01) had a statistically significant effect on survival on multivariate analysis.

 

Conclusions:

Carefully selected patients with multiple metastases or high volume intracranial metastatic disease have acceptable survival outcomes following stereotactic radiosurgery. Increasing volume of disease and non-small cell lung cancer primaries negatively affects survival, while the use of intracranially active systemic therapy is associated with improved survival.


Hamoun ROZATI (London, United Kingdom), Ian PADDICK, Ian SABIN

16:30-17:30
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C19
ORAL PRESENTATION
Body SRS/SBRT (1)

ORAL PRESENTATION
Body SRS/SBRT (1)

Moderators: Laura LOZZA (Responsible Breast Tumor Radiotherapy) (Milano, Italy), Alexander MUACEVIC (Director) (Munich, Germany)
16:30 - 16:40 #30108 - OP31 Stereotactic Body Radiation Therapy (SBRT) for lung metastasis from Soft Tissue Sarcoma (STS): results of a phase 2 clinical study.
OP31 Stereotactic Body Radiation Therapy (SBRT) for lung metastasis from Soft Tissue Sarcoma (STS): results of a phase 2 clinical study.

Background: Soft-tissue sarcomas (STS) are a rare group of malignancies, accounting about 1% of all cancers in adults. Many patients with STS develop metastatic disease, and lung is the most frequent site of distant spread of disease (18-35%). Although surgery is the main modality used, more recently Stereotactic Body Radio Therapy (SBRT) is emerging as an effective alternative  with comparable results in term of local control,  but to date no consolidate data exist regarding the effective role of SBRT. Based on this background we designed a prospective phase 2 study aiming to evaluate the efficacy of SBRT for lung metastases from STS.

Materials and Methods: Patients aging 18-85 years, good PS, confirmated STS diagnosis, up to 4 metastatic lung lesion with maximum tumor diameter ≤5cm, were enrolled. Total doses prescribed were 30 Gy/1 fr for peripheral lesions ≤10 mm, 60 Gy/3 fr for peripheral lesions between 10-20 mm, 48 Gy/4 frs for peripheral lesions 20-50 mm, and 60 Gy/8 fr for central lesions. Clinical outcome was evaluated by thoracic and abdominal CT scan 2 months after SBRT and every 3 months thereafter. Tumor response was defined using European Organization for Research and Treatment of Cancer Response Evaluation Criteria in Solid Tumors (EORTC-RECIST1.1). Toxicity was recorded using Common Terminology Criteria for Adverse Events version 4.2.

Results: Between January 2015 and December 2020, 44  patients for 71 lung lesion treated were evaluated. The majority had leiomyosarcoma histology (13), grade 3 (28) sarcoma, and limbs location (18). Pulmonary metastases were present at diagnosis in 6 patients, while others developed lung lesion at a median time of 24 months (range 4-282 months). The median follow-up time  from SBRT was 48 months (12–154  months). No severe toxicity (grades III–IV) was recorded, and no patients required hospitalisation. The 5-years local control rate (from SBRT treatment) was 93%. Overall survival at 2 and 5 years was 66.2% and 48%, respectively.  On univariate and multivariate analysi factors conditioning OS were grade (p=0.0175), interval time from diagnosis to pulmonary lesions occurence (p=0.0416), and the number of metastatic lung lesions (=0.0076). At last observation time  26 patients (59%) were alive. All other died because of distant progression.

Conclusions: SBRT provides excellent local control of pulmonary metastasis from soft tissue sarcoma (STS) and may improve survival in selected patients. SBRT should be considered for all patients with pulmonary metastasis (PM) and evaluated in a multidisciplinary team.


Beatrice MARINI (Milano, Italy), Pierina NAVARRIA, Elena CLERICI, Davide BALDACCINI, Marco BADALAMENTI, Ciro FRANZESE, Davide FRANCESCHINI, Luisa BELLU, Giuseppe Roberto D'AGOSTINO, Marta SCORSETTI
16:40 - 16:50 #30105 - OP32 Could Stereotactic Body RadioTherapy be a valid option in metastatic lung cancer with oligoprogressive disease?
OP32 Could Stereotactic Body RadioTherapy be a valid option in metastatic lung cancer with oligoprogressive disease?

Purpose or Objective

Oligoprogression (OPD) is defined as a condition where limited progression (1-3 metastases) is observed in patients undergoing systemic cancer treatment. Local treatment of OPD might delay systemic therapy line switch, which could be beneficial in patients experiencing prolonged global disease control with novel targeted or immune therapies. In this study we investigated the impact on outcome of stereotactic body radiotherapy (SBRT) in patients with OPD from metastatic lung cancer.  

Materials and Methods

Data from a cohort of consecutive patients treated with Cyberknife and Linac-based SBRT between June 2015 and August 2021 were collected.  All extracranial metastatic sites of OPD from lung cancer were included. Dose regimens consisted of 24 in 2 fractions, 30-51 Gy in 3 fractions, 30-55 Gy in 5 fractions, 52.5 Gy in 7 fractions and 44-56 Gy in 8 fractions. Dose was expressed as Biological Effective Dose for α/β=10 (BED10). Kaplan-Meyer method was used to calculate Overall Survival (OS), Local Control (LC) and Disease Progression-free Survival (DPFS) from the start date of SBRT to event.

Results

Sixty-three patients, 34 female and 29 male were included. Median age was 75 years (range 25–83). All patients received concurrent systemic treatment before the start of the SBRT: 19 chemotherapy (CT) alone (30%), 26 CT plus immunotherapy (IT) or plus Tyrosin kinase inhibitors (TKI) (41%) and 18 IT/TKI alone (29%).  SBRT was delivered to lung (n=29), mediastinal node (n=9), bone (n=7), adrenal gland (n=19), other visceral metastases (1) and other node metastases (n=4). A median BED10 of 104 (range 39-151) Gy10 was delivered.  After a median follow up of 20 months (range 1-48), median overall survival  was median OS was 23 months (figure 1). LC was 93% at 1 year and 87% at 2 years. DPFS was 7 months. At univariate analysis, age, type of systemic treatment, metastatic site receiving SBRT and BED were not significant prognostic factors for overall survival. 

Conclusion

SBRT in lung cancer patients for oligoprogression resulted in a long median OS of 23 months. One-year LC was 93%. Median DPFS was 7 months, translating into continuation of effective systemic treatment as other metastases grow slowly. SBRT could be useful to postpone the change of chemotherapy and/or immunotherapy. More research is needed to select OPD patients eligible for SBRT.

 


Michele AQUILANO (Firenze, Italy), Mauro LOI, Lorenzo LIVI, Joost NUYTTENS
16:50 - 17:00 #30211 - OP33 Single fraction SABR for lung oligometastases guided by artificial intelligence real time tumor tracking on helical Radixact.
OP33 Single fraction SABR for lung oligometastases guided by artificial intelligence real time tumor tracking on helical Radixact.

Aims: Herein we report preliminary results of a pilot study of single fraction SABR in elderly and multiple lung oligometastatic patients. This study investigates the feasibility and the compliance to lung radiosurgery. 

Materials: Lung tumor tracking allows to reduce the healthy tissue irradiation and is theoretically faster than the gating technique. Single fraction SABR in lung nod- ules is established as an appropriate treatment in oligometastatic patients. However, the risk of target missing in single fraction is higher than in fractionated SABR. Recently and only present in few centers worldwide, Accuray Int, developed a free breathing real time tumor tracking based on artificial intelligence for helical IMRT delivery (Synchrony on Radixact system). 28 Gy single fraction SABR was planned in 10 patients in both peripheric and central lesions. In room time, nodule volumes, local response, real time tracking verification have been assessed for all the patients involved. 

Results: Mean patients age was 79 years old (75-84) and 7 ones were men and the remaining 3 were women; in all cases their PS was 0. All patients had oligometastatic disease: primary melanoma (5), primary NSCLC (2) and CRC (1), HCC (1) and sarcoma (1). Concurrent immunotherapy (respectively Pembrolizumab, Nivolumab and Ipilimumab) was delivered in 6 patients. Lesions were both central (5/10) that peripheral (5/10). Mean GTV volume was 8,50 cc (from 1,9 cc up to 18,2 cc), minimum diameter of lesions was 129 mm to 312 mm. Median beam on time was 17,6 min (910 sec – 1255 sec). The analysis of the cumulative vector of nodules movement, measured a median excursion of 7 mm with a median respiratory cycle time of 4 seconds. No lesions progressed, due to the short follow up, the shrinkage time-volume plot is currently under evaluation. Median follow-up was 8 months, during which we observed no clinical acute toxicity, four patients showed a radiological pattern of diffuse consolidation. All the lesions reduced their volume from 40% up to 90%. For those patients with a follow-up longer than 1 year, no relevant toxicity was radiologically reported.

Conclusions: The preliminary results of our pilot study, showed that lung SABR executed throughout Synchrony on Radixact system is a high compliance treatment in elderly oligometastatic patients. This advanced technique needs a high expertise of all the per- sonnel but is very promising in specific cohort of patients.


Stefano VAGGE (Genova, Italy), Marco GUSINU, Zefiro DANIELE, Genova CARLO, Spagnolo FRANCESCO
17:00 - 17:10 #29467 - OP34 Preoperative robotic stereotactic radiotherapy in early breast cancer: phase II ROCK trial (NCT03520894).
OP34 Preoperative robotic stereotactic radiotherapy in early breast cancer: phase II ROCK trial (NCT03520894).

Background

Breast-conserving surgery (BCS) followed by postoperative radiation therapy (RT) to the residual breast represents the current standard of care for most women affected by early breast cancer. However, standard postoperative regimens are characterized by postsurgical waiting time and potential acute and late locoregional adverse events. Several studies suggested that breast cancer cells can be more sensitive to high doses administered in short intervals. Preoperative robotic stereotactic radiotherapy (SBRT) followed by BCS may yield potential advantages in selected patients. An exploratory phase II study (ROCK trial – NCT03520894) was conducted in our institution.

Materials

Women with histologically proven unifocal invasive hormonal receptors positive, HER2 negative breast cancer, sized less than 25 mm, with negative clinical nodal status, aged 50+ and eligible for BCS were enrolled. Fiducial markers were introduced in peri/intralesional position. Magnetic resonance imaging (MRI) was used in addition to standard CT-based planning. Patients received 21 Gy in single fraction with CyberKnife® followed by BCS two weeks after preoperative SBRT. The primary endpoint was the acute skin toxic effect rate. Secondary objectives were the pathological response rate and the late adverse events rate. Echocardiography and spirometry were performed before preoperative SBRT and yearly thereafter. Translational research was conducted to identify correlations between radiogenomic, immunological and biochemical biomarkers with treatment-related response and toxicity.

Results

From August 2018 to September 2021, a total of 70 patients were screened on mammography; 29 of them were eligible following inclusion criteria. Seven were excluded due to multiple foci disease at basal MRI, and 22 patients were successfully treated. All required dosimetric parameters and normal tissue constraints were met in all cases. Median age at diagnosis was 68 years (range 50-86) and median tumor size was 13 mm (range 7.5-25). All treated patients received surgery within 14 days from preoperative SBRT without any delay or complication. No patients experienced acute skin toxicity of grade (G) 2 or higher; only one patient had a G1 erythema one month after BCS. Two patients reported a pathological complete response, according to Chevallier’s classification. At a median follow up of 18 months, no patients experienced locoregional recurrence or distant metastases. No clinically meaningful changes were observed regarding left-ventricular ejection fraction and spirometric parameters.

Conclusion

Results from the ROCK trial showed that single fraction preoperative robotic SBRT is a feasible technique in selected breast cancer patients with a good safety profile and encouraging activity. This new approach warrants further investigations.


Luca VISANI, Viola SALVESTRINI (Florence, Italy), Icro MEATTINI, Carlotta BECHERINI, Isacco DESIDERI, Erika SCOCCIMARRO, Vanessa DI CATALDO, Monica MANGONI, Chiara BELLINI, Jacopo NORI, Marco BERNINI, Lorenzo ORZALESI, Luis SANCHEZ, Simonetta BIANCHI, Raffaella DORO, Laura MASI, Lorenzo LIVI
17:10 - 17:20 #29915 - OP35 Stereotactic body radiotherapy (SBRT) and concomitant systemic therapy in oligoprogressive breast cancer patients.
OP35 Stereotactic body radiotherapy (SBRT) and concomitant systemic therapy in oligoprogressive breast cancer patients.

Purpose: breast cancer is a heterogenous disease with a deep tailoring level. Evidence is accumulating on the role of stereotactic body radiotherapy (SBRT) in the management of oligometastatic disease, however this is limited in breast cancer. The aim of the present study is to show the effectiveness of SBRT in delaying the switch to a subsequent systemic treatment in oligoprogressive breast cancer patients.

Methods and materials: retrospective analysis from two Institutions. Primary endpoint: time to next systemic treatment (NEST). Secondary endpoints: freedom from local progression (FLP), time to the polymetastatic conversion (tPMC) and overall survival (OS).

Results: One-hundred fifty-three (153) metastases in 79 oligoprogressive breast cancer patients were treated with SBRT. Median follow-up 24 months. Median NEST 8 months. Predictive factor of NEST at the multivariate analysis (MVA) was the number of treated oligometastases (HR 1.765, 95%CI 1.322-2.355; p=0.00). Systemic treatment after SBRT was changed in 29 patients for polymetastatic progression and in 10 patients for oligometastatic progression 70Gy10 was associated with improved FLP (90% versus 74.2%). The median tPMC was 10 months. At the MVA the only factors significantly associated with tPMC were the number of oligometastases (HR 1.172, 95%CI 1.000-1.368; p=0.03), and the local control of the treated metastases (HR 2.726, CI95% 1.108-6.706; p=0.02).

Conclusions: SBRT can delay the switch to a subsequent systemic treatment, however patient selection is necessary. Several predictive factors for treatment tailoring have been identified.


Luca NICOSIA (ITALY, Italy), Vanessa FIGLIA, Nicola RICOTTONE, Francesco CUCCIA, Rosario MAZZOLA, Niccolò GIAJ-LEVRA, Francesco RICCHETTI, Michele RIGO, Fatemeh JAFARI, Stefano Maria MAGRINI, Andrea GIRLANDO, Filippo ALONGI
17:20 - 17:30 #29441 - OP36 Five fractions schedule radiotherapy for early breast cancer with simultaneous intergraded boost. Our early single-institution experience.
OP36 Five fractions schedule radiotherapy for early breast cancer with simultaneous intergraded boost. Our early single-institution experience.

Background: Adjuvant breast radiotherapy practice standard is 40 Gray in 15 fractions. 10 patients with early breast cancer were treated after primary surgery, with ultra-hypofractionated 5 fractions in one week schedule WBI regimen of 26 Gray (Gy), based on the FAST FORWARD trial results, and 0,6Gy/fraction of simultaneous integrated boost (SIB) for a total dose of 29Gy/5,8Gy delivered in 5 fractions. This study attempts to identify the safety, low toxicity profile and patient convenience compared to other hypofractionated schemes.

Methods: In the present study, 10 cases of patients, aged 40-70 with invasive carcinoma of the breast T1–2, pN0, M0 who underwent radiotherapy after breast conservation surgery are presented. Concurrent trastuzumab and/or endocrine therapies were allowed. For patient participation, all the inclusion criteria of the FAST FORWARD trial were met. 26 Gy in five fractions to the whole breast, with SIB of 29Gy to the tumor bed over one week, was delivered. At the breast conservation surgery, two pairs of titanium clips were implanted into the walls of the tumour excision cavity (tumor bed) to assist target delineation. Planning Target Volumes PTVwb and PTVTB were created by adding a 3d uniform expansion of 10mm to the CTVwb and 5mm to the CTVboost containing the tumour bed (clips), respectively. For dose-volume histogram assessment, lungs, heart, contralateral breast, and ipsilateral ribs were contoured. VMAT treatment plans using 6MV beams were used for the patient treatment. Daily pretreatment imaging verification was performed (CBCT), and all corrections were applied (6dCouch). Ultrasound examination and photographs were taken as baseline before the treatment. Follow-up assessment performed in week 1, week 4 and then every 3 months.

Results: All patients completed the 5 fractions schedule. The titanium clips proved to be necessary for the accuracy of the tumor bed delineation. The prescription dose was uniformly delivered to the whole breast and the tumor bed (V95%(PD)>95%). All dose constraints for OARs described by Fast-Forward trial were met. During the first year follow up, no changes in breast appearance or shape were observed, while the skin reaction was grade 2 or less.

Conclusions: WBI regimen of 26 Gy in 5fx with SIB is a well-tolerated and safe hypofractionated radiotherapy scheme. It is also time efficient as it reduces the overall treatment time of EBRT to 1 week, with no differences in normal tissue toxicity or changes in breast appearance versus other radiotherapy schemes. 


Georgios KRITSELIS (ATHENS, Greece), Fiorita POULAKAKI, Ioannis FLOROS, Chrysoula STEFANIDOU, Katerina SILIVRIDOU

17:30
17:30-18:30
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B15
SPONSORED SYMPOSIUM

SPONSORED SYMPOSIUM

17:30-18:30
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C15
SPONSORED SYMPOSIUM

SPONSORED SYMPOSIUM