Tuesday 11 June
07:30

Tuesday 11 June

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B31
07:30 - 09:00

BREAKFAST SEMINAR
QUALITY OF LIFE: WHAT THE DATA SHOWS

Moderators: Allisson Barcelos BORGES (Radiation Oncologist) (Brasilia-DF, BRAZIL), Joao Gabriel GOMES (BRAZIL), Jonathan KNISELY (Lake Success, USA)
07:30 - 07:50 Gliomas: What is Best for the Patient. Bente Sandvei SKEIE (MD, PhD) (Bergen, NORWAY)
07:50 - 08:10 Metastases & Neurocognition: An Update. Jeff WEFEL (Associate Professor, Chief, Section of Neuropsychology) (Houston, USA)
08:10 - 08:30 Skullbase Lesions: Is SRS/SRT Better Than Surgery? Oystein TVEITEN (Consultant neurosurgeon) (Bergen, NORWAY)
08:30 - 08:50 Risk of Radiation-Associated Intracranial Malignancy after SRS for Benign Tumors. Matthias RADATZ (Director) (Sheffield, UK)
Segovia I

Tuesday 11 June

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C31
07:30 - 09:00

BREAKFAST SEMINAR
PROSTATE SBRT

Moderators: Sebastiao CORREA (RADIO-Oncologist) (São Paulo, BRAZIL), Ciro FRANZESE (MD) (Milano, ITALY), Luis LARREA (Director) (Valencia, SPAIN)
07:50 - 08:10 Clinical Results. David PRYOR (Radiation Oncologist) (Brisbane, AUSTRALIA)
08:10 - 08:30 Quality of Life in prostate SBRT. Maris MEZECKIS (radiation oncologist) (Sigulda, LATVIA)
08:30 - 08:50 Quality Assurance. Anderson PASSARO (BRAZIL)
El Pardo I

Tuesday 11 June

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A31
07:30 - 09:00

BREAKFAST SEMINAR
PEDIATRIC BRAIN RADIOSURGERY

Moderators: Leonardo FRIGHETTO (Neurosurgeon) (Porto Alegre, BRAZIL), Paul W. SPERDUTO (2HBK7YS$) (Minneapolis, USA), Amanda DE OLIVEIRA LÓPES (BRAZIL)
07:30 - 07:45 Craniopharyngioma Combined Approach - Surgery and Radiosurgery. Jorge BIZZI (BRAZIL)
07:45 - 08:00 Efficacy, Outcomes, and new directions. Shannon FOGH (Radiation Oncologist) (San Francisco, USA)
08:00 - 08:15 Long Term Outcomes: Brain Tumors. Erin MURPHY (Radiation Oncologoy) (Cleveland, USA)
08:15 - 08:30 #17732 - a31-4 Radiosurgery for Paediatric AVM - A Single Centre Experience in 50 consecutive Patients.
a31-4 Radiosurgery for Paediatric AVM - A Single Centre Experience in 50 consecutive Patients.

BACKGROUND: Gamma Knife (GK) radio surgery for paediatric arteriovenous malformations (AVM) of the brain presents a non-invasive treatment option. Age has a potential influence on the characteristic presentation of these AVMs and their ultimate outcome. We report our institutional experience with GK for paediatric AVMs.

METHODS: We performed a retrospective review of 50 consecutive paediatric patients diagnosed with cerebral AVMs and treated with GK at our institution from January 2014 to and December 2016. Patient demographics, AVM characteristics, treatment parameters and AVM responses were recorded.

RESULTS: The commonest presentation was with headache in 70% of these patients , followed by bleed (24%) and 20% of these patients had seizures.AVMs were mostly located in the right-side seen in 18 patients. Mean nidus volume was around 3.6 cc with almost 44% of these patients had small AVMs corresponding to SM grading 1, 2 while remaining were SM grade 4,5.  Most of these patients were treated with primary GK (82%), while 9 patients received  secondary GK (6  post embolisation and 3 post surgery) for AVM. A minimum follow up period of two years showed almost 70% of patients had complete .elimination of the lesion. Rest of these patients had lesions reduced in volume. During the initial 6 months,  5 patients had weakness and focal neurological deficits but with close follow up and monitoring there was improvement.

 CONCLUSIONS: GK radio surgery for paediatric AVMs offers a safe and effective treatment option, with good obliteration rate.

Shweta KEDIA (New Delhi, INDIA), Atmanranjan DASH, Deepak AGARWAL, Manmohan SINGH, Rajinder THAYLLING, Shashank KALE
08:30 - 08:45 #17544 - a31-5 Extracranial dose measurements in paediatric patients receiving radiosurgery and the risk of radiation-induced malignancy.
a31-5 Extracranial dose measurements in paediatric patients receiving radiosurgery and the risk of radiation-induced malignancy.

Background: Any medical procedure utilising ionising radiation carries a risk of developing a radiation-induced malignancy. The risk of developing extra-cranial malignancies is believed to be low in Gamma Knife Radiosurgery (GKRS) but few studies have been conducted which attempt to quantify this risk. Paediatric patients treated for Arteriovenous Malformations (AVMs) are of particular concern due to the non-malignant nature of their disease, increased risk of malignancy and their longer life expectancy.

Methods: Thermoluminescent dosimeter (TLD) measurements were conducted in 17 patients treated with GKRS for AVMs (9 Females and 8 Males, mean age at treatment = 12). Three sets of TLDs were positioned anteriorly on the skin of each patient at the levels of the thyroid, breast and pelvis. Each set was comprised of 10 TLDs, 5 Lithium Fluoride detectors and 5 Germanium-doped glass fibres. These were calibrated, annealed, handled and read-out in line with good practice procedures yielding a dose uncertainty of approximately 5%.  The average dose measured by each TLD set was used to approximate the doses delivered to individual organs in each patient’s body. Individual patient doses were then used in a radiation risk assessment tool (RadRAT) to calculate each patient’s Lifetime Excess Risk (LER) of developing malignancies due to the radiation exposure.

Results: The mean doses measured were 17.7 mGy, 7 mGy and 0.17 mGy for the neck, chest and pelvic areas respectively. The mean LER was calculated to be 0.18% on average and ranged from 0.04% to 0.41% between patients.

Conclusion: Considering the baseline cancer risk in this group of patients (»35%), the additional LER of body malignancy contributed by the GKRS exposure is acceptable when balanced against the possible risks from not treating the AVM.

Alexis DIMITRIADIS (London, UK), Amjad ALYAHYAWI, Alison CAMERON, Neil KITCHEN, Gregory JAMES, Ian PADDICK
08:45 - 09:00 The risk of oncogenesis. Andrey GOLANOV (Head of the Department) (Moscow, RUSSIA)
Segovia II-III-IV
09:00

Tuesday 11 June

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A32
09:00 - 10:15

PARALLEL SESSION
SPECIAL SYMPOSIUM: IMMUNOTHERAPY & SRS/SBRT

Moderators: Michael LIM (Professor of Neurosurgery) (Baltimore, USA), John SUH (Radiation Oncologist) (Cleveland, USA), Leonardo VIEIRA (Doctor) (Recife, BRAZIL)
09:00 - 09:15 Immunology for the Oncologist. James WELSH (Chicago, USA)
09:15 - 09:30 Clinical Application in Brain: What we know. Michael LIM (Professor of Neurosurgery) (Baltimore, USA)
09:30 - 09:45 Clinical Application in Lung: What we know. To Be CONFIRMED
09:45 - 10:00 What We Don't Yet Know: Key Issues. Paul W. SPERDUTO (2HBK7YS$) (Minneapolis, USA)
10:00 - 10:15 Clinical Trials & Research Summary. Daniel TRIFILETTI (Assistant Professor) (Jacksonville, USA)
Segovia II-III-IV

Tuesday 11 June

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B32
09:00 - 10:15

Oral Session
PHYSICS #2

Moderators: Fernando JAPIASSU (BRAZIL), Anderson PASSARO (BRAZIL), David SCHLESINGER (Medical Physics) (Charlottesville, USA)
09:00 - 09:10 #17753 - b32-1 A phase-space source model for Monte Carlo dosimetry calculations in Gamma Knife clinical applications.
b32-1 A phase-space source model for Monte Carlo dosimetry calculations in Gamma Knife clinical applications.

Purpose: To develop a phase space source model enabling Monte Carlo (MC) dosimetry calculations and verification of Gamma Knife treatments in inhomogeneous geometries.

Materials and methods: A previously validated Gamma Knife Perfexion (GKPFX) MC-based detailed source model was used to create single sector phase-space (PHSP) source models for the three available collimators.  These were validated in terms of single sector and single shot X-Y-Z dose profiles in a spherical water phantom with corresponding data obtained using the detailed model and experimental EBT-3 film measurements.

The PHSP-source model was subsequently used to validate GammaPlan (LGP) dose predictions using the convolution algorithm for a plan using a composite shot consisting of all collimator sizes delivered in a virtual phantom of 8 cm radius containing a 1.5 cm thick hemispherical bone inhomogeneity in the vicinity of the 50% isodose line.

Results: Single sector and single shot dosimetry results using PHSP simulations were found in excellent agreement with corresponding detailed MC model calculations and film measurements. Indicatively, gamma passing rates above 99.5% were achieved for local 1%/1mm criteria against detailed model simulation and 2%/1mm criteria against film measurements. Efficiency gain by a factor of up to 2500 for the smaller field size was attained compared with detailed model simulations. Convolution absolute dose distribution evaluation using the PHSP-source model simulations in the inhomogeneous phantom resulted in a gamma passing rate of 99.15%, applying 1%/1mm local gamma index criteria and 1% dose threshold.

Conclusion: An accurate and efficient GKPFX single sector PHSP source model was developed and validated. LGP calculations using the convolution algorithm were evaluated in an inhomogeneous geometry using this model and found to be in excellent agreement, indicating the accuracy of the convolution algorithm in water-bone inhomogeneities. Further work on convolution algorithm verification on more complex and clinical cases is in progress.

Andreas LOGOTHETIS, Evangelos PANTELIS, Emanouil ZOROS, Eleftherios PAPPAS, Georgios KOLLIAS, Alexis DIMITRIADIS, Ian PADDICK, Jonas GARDING, Jonas JOHANSSON, Pantelis KARAISKOS (Athens, GREECE)
09:10 - 09:20 #17644 - b32-2 Evaluation of PTW microdiamond edge-on orientation for small field dosimetry.
b32-2 Evaluation of PTW microdiamond edge-on orientation for small field dosimetry.

The IAEA TRS-483 code of practice requires that solid state dosimeters used for quality assurance in small field radiotherapy be utilized in a “face-on” orientation [1]. However, this practice means that the high spatial resolution of the PTW microdiamond or uD in “edge-on” orientation is unrealized [2]. The aim of this study was to characterize the uD for small field applications in an edge-on orientation. To that end, the detector went through a rigorous characterization of its performance in both edge-on and face-on orientations for different field sizes and angular incidences

Output factor (OF), Percentage Depth Dose (PDD) curves and field profile measurements were performed with the uD in edge-on and face-on orientations and compared against the IBA RAZOR for 6MV photon field for both FF/FFF modalities in a IBA blue water phantom on a Varian True Beam linac for square field sizes between 0.5-10 cm. Angular dependence as a function of field size measurements (0.5x0.5-3x3cm2) were also performed in two different cylindrical PMMA phantoms to investigate the effect of orientation upon angular dependence.

The high spatial resolution of the uD in edge-on, allowed for precise profilometry of small FF/FFF square fields to be performed. The uD was shown to over-response in edge-on in comparison with face-on for fields ≤2x2cm2. Angular dependence measurements in the cylindrical edge2face phantom showed a 6-12% difference in response of the uD in the edge-on and face-on orientations for 0.5-3cm square fields, although larger variations (~31%) were observed. Additional angular dependence measurements in the cylindrical edge2edge phantom shows that the uD is almost angular independent over a range of 180° with differences of ±1%.

In edge-on orientation, the uD was shown to be suitable for profile reconstruction as well as exhibiting negligible angular dependence (±1%) making it an option for specific clinical applications. However, the orientation is deemed to be unsuitable for PDD and OF measurements, due to a less than ideal build-up behaviour and over-response. Full results including that of a dedicated Monte Carlo simulation study to optimise the detector packaging will be presented at the ISRS congress.

[1] H. Palmans, et al, Technical Report Series No. 483. International Atomic Energy Agency, Vienna; 2017

[2] V. De Coste, et al, Phys. Med. Biol. 62 (2017) 7036-7055

Jeremy DAVIS (Gywnneville, AUSTRALIA), Sultan ALHUJAI, Owen BRACE, Dean WILKINSON, Duncan BUTLER, Jason PAINO, Brad OBORN, Michael LERCH, Marco PETASECCA
09:20 - 09:30 #17682 - b32-3 Comparison of planning techniques for linac-based stereotactic radiosurgery in patients with 4 up to 10 brain metastases.
b32-3 Comparison of planning techniques for linac-based stereotactic radiosurgery in patients with 4 up to 10 brain metastases.

Purpose/Objective:Stereotactic radiosurgery (SRS) is a promising treatment option for patients with 4 to 10 brain metastases (BM). We studied whether automated planning can improve LINAC-based stereotactic radiosurgery plan quality for multiple BM. 

Materials/Methods:For 12 patients with 4 to 10 BM, five non-coplanar LINAC-based SRS plans were created for 6MV photons: a manually planned dynamic conformal arc (DCA) plan with a separate isocenter for each metastasis, a dynamic IMRT plan with one isocenter, a VMAT plan with one isocenter, two DCA plans with one isocenter for three and five couch rotations. The last three plans were automatically generated. The prescription dose was 21Gy or 18Gy single fraction or 25.5Gy in 3 fractions depending on the volume of the largest metastasis and prescribed to the 80% isodose line.The PTV coverage should be at least 98%.To assess SRS plan quality, the Paddick conformity index (CI), the Paddick gradient index (GI), the total V12Gy and V5Gy and the number of monitor units (MU) were studied. 

Results: The mean CI was the highest for dynamic IMRT and manual DCA plans. The lowest GI was for manual DCA plans with a separate isocenter for each metastasis and for automatically generated DCA plans with one isocenter, the highest GI was for VMAT plans. The V12Gy of automatically generated DCA plans with one isocenter and dynamic IMRT plans were comparable with the manual DCA plans. The number of MU was the smallest for VMAT plans, followed by IMRT and automatically generated DCA plans.

Conclusions: Automatically generated LINAC-based, single isocenter SRS plans for multiple BM result in fewer MUs, with a plan quality comparable to manual multiple-isocenter DCA plans. Based on all compared parameters, dynamic IMRT and DCA plans with one isocenter were the best and comparable with multiple-isocenter DCA plans. 

Ruud WIGGENRAAD (Leidschendam, THE NETHERLANDS), Anna PETOUKHOVA, Roland SNIJDER, Linda DE BOER-DE WIT, Ivonne MUDDE-VAN DER WOUDEN, Mireille FLORIJN, Jaap ZINDLER, Jan VAN SANTVOORT
09:30 - 09:40 #17810 - b32-4 Accuracy of frameless image guided stereotactic radio-surgery for brain metastases.
b32-4 Accuracy of frameless image guided stereotactic radio-surgery for brain metastases.

Objectives: To evaluate inter- and intra-fraction motion detected using frameless immobilization for Gamma Knife (GK) stereotactic radiosurgery (SRS).

Materials and Methods: Following consent to frameless GK-SRS, patients were immobilized with a thermoplastic mask followed by acquisition of a reference CBCT scan. Daily setup verification and intra-fraction motions were monitored using CBCT and an intra-fractional motion management (IFMM) system.  Patient setup and CBCT was repeated when IFMM thresholds were exceeded or when the patient needed a voluntary break. In-house Matlab scripts were developed to parse log files to determine patient inter- and intra-fraction setup variability.

Results: Thirty-eight plans were reviewed from 36 patients (2 patients treated twice). The average number of targets per plan was 1.3 [range: 1-4] and treatment time was 42 min [range: 8.3 - 145.9min]. The number of CBCT per fraction is 1.8 [range: 1-7]. Systematic setup error was found by the difference between reference and daily CBCTs as 0.93, 1.17, 1.17 mm and 0.8, 0.6, 2.2 degrees in x, y, and z direction respectively. Random error (intra fraction) was found 0.40, 0.33, 0.35mm and 0.3, 0.3, 0.6 degrees from successive CBCTs. IFMM measurement with marker motion larger than 0.2mm are  77 times/min during beam delivery and the average directional motion during beam on was 0.0, -0.1, 0.3mm (standard deviation of 0.4, 0.4, and 0.6mm) in x, y, and z direction. Systematic (random) motion of IFMM was 0.7mm, 0.5mm, 0.9mm (0.3, 0.2, and 0.5mm).

Conclusions: Preliminary analysis suggests good setup reproducibility with the largest discrepancy in the z-direction. After setup correction, random intra-fraction motion was found to be within 0.5mm with larger systematic motions triggered for pause or correction by the IFMM.

Young-Bin CHO (Toronto, CANADA), Winnie LI, Normand LAPERRIERE, David SHULTZ, Caroline CHUNG, Barbara-Ann MILLAR, David JAFFRAY, Catherine COOLENS
09:40 - 09:50 #17882 - b32-5 Use of non-composite shots for robust planning in Gamma Knife Icon mask-based treatment.
b32-5 Use of non-composite shots for robust planning in Gamma Knife Icon mask-based treatment.

Purpose: Adapting manufacturer’s end-to-end test to the Gamma Knife Icon mask system, we were able to verify the accuracy of position correction in Gammaplan even for large angular and translational shifts. However, the test does not verify if isodose volume is preserved.

Methods and Materials: An anthropomorphic head phantom with a film insert in the mid-coronal plane is used. Lesion-E has an elliptical shape covered by one single composite shot. Lesion-S has a sausage shape covered by 4 composite shots. Close to either lesion are organs at risk (OAR1 and OAR2). For each lesion, a non-composite plan was also created to produce similar prescription isodose volume with comparable dose to OARs. The phantom was treated in the planning position (A), and in a position shifted 4 cm superiorly and rotated 95 degrees to right (D). For lesion-S, the phantom was irradiated in two additional positions: 14-degree chin-up (B), and 14-degree rotation to right with 7-degree chin-up (C). (Min, max, mean) dose reported under dose evaluation during treatment were analyzed. Gamma Index comparison of film dose at positions B, C, or D versus A was used. Prescription dose was 3 Gy per fraction.

Results: Non-composite-shot plans: All Gamma Index passing rates are > 97%, and all differences in (min, max mean) dose are <= 0.1 Gy. Composite-shot plans: Passing rate is 57% for position D for lesion-E, and 92%, 78%, and 44% for position B, C, and D, respectively for lesion-S. The difference in (min, max, mean) doses becomes larger as the phantom shifted from position B through D: from a maximum 0.4-Gy difference in position-B to a maximum difference of 0.8-Gy in position-D for lesion-S and as large as 1.4 Gy for lesion-E.

Conclusions: For robust planning, it is recommended to use only non-composite shots for mask-based treatments with Icon.

Dershan LUO (Houston, Texas, USA), Eun HAN, Xin WANG, Tina BRIERE
09:50 - 10:00 #17785 - b32-6 End-to-End dosimetric and geometric accuracy of linac-based high-definition dynamic stereotactic treatments for multiple metastases: A multi-institutional study.
b32-6 End-to-End dosimetric and geometric accuracy of linac-based high-definition dynamic stereotactic treatments for multiple metastases: A multi-institutional study.

Objective:

Dosimetric and geometric accuracy are paramount in Stereotactic Radiosurgery (SRS) to achieve effective and safe implementation of the treatment. In this work, End-to-End accuracy was evaluated for single-isocenter multi-focal SRS treatments in six centers.   

Methods:

Eight identical 3D-printed head phantoms were constructed using the planning-CT dataset of a patient, simulating bone structures by a bone equivalent material. Six phantoms (one per clinic) were filled with 3D polymer gel, which simulates brain tissue and acts as a dosimeter in combination with an MR scanner, while the other two phantoms were filled with water and equipped with an ion chamber and a film insert, respectively. A single-isocenter plan using a 5-arc VMAT beam arrangement was created in Monaco Treatment Planning System (TPS). Six targets were adjusted to achieve a range of target sizes 6-25mm in diameter at various distances from the isocenter. Prescription dose was set to 8Gy and dose delivery was performed by the Elekta Versa HD-HDRS linear accelerator with HexaPOD system, following departments’ clinical SRS workflow. Point, 2D, and 3D dose values were obtained by ion chamber, film, and gel measurements, respectively. Geometric accuracy of all targets was evaluated by the comparison of 2D/3D relative dose distributions between measurements and TPS calculations. Dosimetric accuracy was verified by ion chamber measurements in one target.     

Results:

Excellent geometric agreement (<1mm) between TPS calculations and measurements was observed for the targets lying less than 4cm from the isocenter. For the targets with a distance from the isocenter greater than 4cm, the average difference from all sites was 0.8mm with a maximum discrepancy of 1.9 mm. Ion chamber measurements yielded an average difference of 1.2% ± 0.5% leading to a superb agreement within uncertainties.   

Conclusion:

The overall accuracy of single-isocenter multi-focal SRS treatments was found within acceptable limits for all clinics using a patient-specific End-to-End methodology.

Emmanouil ZOROS (Athens, GREECE), Daniel SAENZ, Kyveli ZOURARI, Michael REINER, Lip Teck CHEW, Samuel HANCOCK, Alex NEVELSKY, Christopher F NJEH, Niko PAPANIKOLAOU, Evangelos PAPPAS
Segovia I
10:15 COFFEE BREAK - POSTERS & EXHIBITION
10:45

Tuesday 11 June

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A34
10:45 - 11:15

PARALLEL SESSION
THE LEKSELL LECTURE

Moderators: Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL), Laura FARISELLI (director) (milano, ITALY), Ian PADDICK (Physicist) (London, UK)
10:45 - 11:15 Gamma Knife Radiosurgery from Leksell to the Present: An Insider’s View. Christer LINDQUIST (Medical co-director) (LONDON, SWEDEN)
Segovia II-III-IV

Tuesday 11 June

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C34
10:45 - 11:45

Oral Session
THORACIC & GASTRO-INTESTINAL

Moderators: Rui HADDAD (BRAZIL), David PRYOR (Radiation Oncologist) (Brisbane, AUSTRALIA), Ben SLOTMAN (Professor and Chairman) (AMSTERDAM, THE NETHERLANDS)
10:45 - 10:54 #17660 - c34-1 Dynamic tracking SBRT (DTSBRT) for the treatment of primary and/or metastatic lung cancer.
c34-1 Dynamic tracking SBRT (DTSBRT) for the treatment of primary and/or metastatic lung cancer.

Purpose/Objectives: There are several methods to reduce the effect of respiratory movement in SBRT for lung tumors. One of them is dynamic tumor tracking method, which has the merit over other methods to reduce the treatment time and the pressure of rigid fixation. We have been using this method (DTSBRT) for several years and analyzed the results.

Materials and Methods: Indications were tumors whose respiratory movement was larger than 10mm on planning CT, fit for SBRT, and normal organ dose constraints were met. DTTSBRT was performed using Vero-4DRT (Gimbal-based) and CyberKnife G4 (Robot arm-based). Prescription doses were 50 Gy/ 4 fr/1 wk at the PTV D95%.

Results: Between March 2013 and March 2017, 46 patients received DTT SBRT. Median age was 76.5 (range 41-90), Male to female ratio was 33:13, There were 26  primary tumors and 20 metastatic tumors. More than 90% tumors were located in the lower lobe (42/46). Median follow-up period was 23.7 months (4.6-59.3mos). 29 cases were treated with Vero-4DRT, whereas 17 cases were treated with CyberKnife. Two-year local control rates for primary and metastatic cancers were 95.0% and 94.7%, respectively (n.s). Two-year overall survival rates for primary and metastatic cancers were 84.6% and 75.0%, respectively (n.s.). There were no differences in local control or overall survival between the treatment machines. There was one Grade 3 pneumonitis. No serial organ toxicity has been observed.

Conclusions

DTSBRT for primary and/or metastatic lung cancer has been promising for good local control and overall survival despite that nearly all of the tumors were located in lower lobe, which has been known to be difficult to control.

Katsuyuki KARASAWA (Tokyo, JAPAN), Yumiko MACHITORI, Satoshi KITO, Sara HAYAKAWA, Kaiji NIHEI
10:54 - 11:03 #17713 - c34-2 DIBH implementation for lung SBRT treatment with low cost local solution in Argentina.
c34-2 DIBH implementation for lung SBRT treatment with low cost local solution in Argentina.

With improved outcomes, lung SBRT has begun for early-stage non-small cell lung cancer patients a routinely indication in the thoracic radiation oncology community. At Mevaterapia radiation therapy centre in Argentina we implemented lung SBRT using Deep Inspiration Breath-Hold (DIBH) technique by a local low cost (U$D 4000) spirometer customized for radiation therapy monitoring.

In DIBH treatment protocol, patients are instructed to breathe through a non-invasive naso-oral mask while theirs respiratory patterns are follow in real time using a hand spirometer connected to a portable computer. Normal respiratory (i.e. respiratory frequency, inspiration volume, espiration volume) and deep inspiration variables (i.e. deep inspiration volume, deep inspiration holding time, repeatability of deep inspiration volumes in time) are recorded during CT scans simulation.

CT scan for treatment planning in DIBH is obtained followed by several short DIBH CT scans at the lesion in order to evaluate absolute displacements within DIBH volumes treatment range.

Treatment planning is performed in Eclipse v13.6 using AAA algorithm and carried out through ARIA system in a Varian Trilogy LINAC with Exactrac and 6D couch technology. Time between CT simulation and treatment is around 5 days, prior to treatment a simulation session at LINAC is scheduled.

During simulation session patient is firstly localized using bone structures with Exactrac and positioning is verified by CBCT in DIBH. Treatment parameters are checked with the patient and treatment simulated in order to corroborate treatment applicability and to reduce patient’s anxiety and fears during actual treatment sessions.

Our protocol had been applied in 6 patients over the last 6 months with a total patient’s time in treatment room of 45±15 minutes. CTV localization in DIBH were regular and reproducible over treatment using spirometer monitoring with local technology low-cost solution. In our service this had become first choice protocol for SBRT lung treatment.

Ruben Oscar FARIAS, Leon ALDROVANDI, Florencia MAURI, Augusto ALVA, Federico Javier DIAZ, Maria Liliana MAIRAL, Mabel Edith SARDI, Mara Lia SCARABINO (Caba, ARGENTINA)
11:03 - 11:12 #17747 - c34-3 Artificial Intelligence techniques improve SBRT treatment planning quality.
c34-3 Artificial Intelligence techniques improve SBRT treatment planning quality.

Purpose

Improve SBRT planning quality through application of AI techniques

 

Methods

Pancreas and liver SBRT planning is often challenging due to tolerance limits of the gastrointestinal (GI) structures.  The clinical treatment planning goal is to retain full PTV coverage at lower dose level and as much as ITV coverage at higher dose level after abiding by the GI constraints.  Since the overlap between targets and OARs vary from patient to patient, percentage of target volume covered at high dose levels has to be staged in order to avoid OARs.

We have developed AI techniques to navigate the optimal strategies to achieve high quality plans. The proposed system is based on a reinforcement learning (RL) framework which includes: (1) the planning states, which is designed in a similar fashion to how planners evaluate plans (e.g. constraint satisfaction, target coverage); (2) the planning objective adjustment actions that planners would take to address different planning needs; (3) a reward scheme based on physician’s prescriptions.  The RL strategy follows the state-action-reward-state-action (SARSA) algorithm with limited dimensionality which is designed to ensure coverage and performance.

The training process essentially simulates how the human planner interacts with the planning systems, evaluating planning objectives at different planning stages, taking different actions at different states, and after each action, the planning result is re-evaluated and a reward is assigned accordingly.

Results

16 clinical cases were used to demonstrate the feasibility of this approach: 10 for AI training and 6 for validation. All 6 validation plans satisfy OAR constraints, while maintaining comparable or better target coverage compared to clinical plans. Average AI planning takes 20 minutes vs. 30-60 minutes for manual planning.

 

Conclusions

The proposed AI approach can potentially improve clinical planning efficiency while achieving comparable planning quality.

Q. Jackie WU, Jiahang ZHANG, Chunhao WANG, Yang SHENG, Suradet JITPRAPAIKULSARN, Fang-Fang YIN (Durham, USA), Yaorong GE
11:12 - 11:21 #17768 - C34-4 Clinical experience with calypso tracking in sbrt for pancreatic tumours.
C34-4 Clinical experience with calypso tracking in sbrt for pancreatic tumours.

Pancreatic adenocarcinoma is a deadly disease being the 4th in lethality despite being the 10th in incidence. Additionally, more then 80% of patients are not candidates for surgical resection, and their overall survival with only systemic therapy is around 6 months. SBRT treatments of locally advanced adenocarcinomas of pancreatic head and body are challenging due to difficulties in motion management and in proximity of radiosensitive organs at risk, primarily the duodenum. The Calypso extracranial tracking system uses implanted fiducials to track tumor movement in real time without any additional radiation dose.  At our clinic we percutaneously implant fiducials under CT navigation into a pancreatic tumor and perform a standard simulation two weeks after implantation. The Calypso extracranial tracking system allows us to significantly reduce contribution of target movement to the CTV PTV magin thus reducing tumor target volume compared to delineating contours on a average 4D CT or compared to using abdominal compression. Patients are simulated in a deep inspiration or expiration phase and contoured with the help of MRI. This reduced volume allows us to prescribe higher doses or to reduce the number of fractions while at the same time keeping the probability of toxicity low. Using the Calypso extracranial tracking system has also shown that the pancreas targets have significant movement contribution from peristaltic movement of the GI track, apart from the respiratory movement contribution. We used this technique for all our patients with pancreatic adenocarcenoma since June of 2017, totaling 30 with locally advanced disease (unresectable) with excellent local control rates and long overall survival, rivaling that of patients who underwent surgical resection.

Domagoj KOSMINA (Sveta Nedelja, CROATIA), Hrvoje KAUCIC, Luka NOVOSEL, Adlan CEHOBASIC, Vanda LEIPOLD, Jelena HAJREDINI, Sanja GASPAR, Marica KESER, Ivo PEDISIC, Dragan SCHWARZ, Sasa SCHMIDT, Andreas MACK
11:21 - 11:30 #17821 - c34-5 Prospective duodenal sparing decreases GI toxicity in pancreatic SBRT.
c34-5 Prospective duodenal sparing decreases GI toxicity in pancreatic SBRT.

Purpose

The proximity of the pancreas to the small bowel presents a unique challenge for pancreatic cancer stereotactic body radiation therapy (SBRT). This study explores the safety and effectiveness of a novel approach optimizing pancreatic tumor coverage and duodenal sparing.

Materials/Methods

54 patients with locally advanced pancreatic cancer were treated with SBRT from 2011-2018. Treatment was delivered pre-operatively (N=23), definitively (N=18), adjuvantly (N=5), or for recurrence or palliation (N=7). All patients underwent endoscopic ultrasound-guided gold fiducial seed placement within and adjacent to the tumor. Planning involved a 4D CT scan with oral contrast, used in conjunction with EUS, PET, and diagnostic biphasic CT scans to identify the gross tumor volume (GTV). The planning target volume (PTV) was created by expanding the GTV by 2 mm. The gastrointestinal tract (GIT) included the duodenum, stomach and small bowel. The duodenum, from the pylorus to the 4th segment, surrounding the GTV was delineated. The small bowel was contoured as a bowel bag from the diaphragm to L1. Three 10 Gy fractions, normalized to the 85% isodose surface, were delivered to the PTV on consecutive weekdays using fiducial-based respiratory motion tracking. Dose-volume histogram (DVH) constraints included stomach and duodenal V7Gy <40%, V15Gy < 25%, and V20Gy <15%. D33% for the duodenal circumference was < 20Gy, and duodenal Dmax <27Gy. Additional dose constraints included liver D50%

Results

All patients tolerated and completed treatment and there were no Grade 3 or higher toxicities. There were 6 patients who did not meet the above mentioned GIT relative volume based dose constraints as per the treating physician’s clinical decision. GIT mean max point dose was 2379 cGy (range 383-3156 cGy). Mean dose to 5 cc and 10 cc of the GIT were 1665 cGy (94–2610 cGy) and 1443 cGy (82-2414 cGy), respectively.

Conclusion

We treated 54 patients with our prospective duodenal sparing protocol to improve the therapeutic index. We have shown that our unique way of delineating the bowel and using relative volume based constraints can be as effective as or better than using absolute volume based constraints which are used in most SBRT protocols. 

Prashant VEMPATI (Lake Success, USA), Raymond CHAN, Peter K TAYLOR, Huma CHAUDHRY, Emile GOGINENI, Sewit TECKIE, Rajiv SHARMA, Vincent VINCIGUERRA, Maged GHALY
11:30 - 11:39 #17904 - c34-6 Novel treatment planning technique to facilitate safe pancreatic SBRT dose escalation.
c34-6 Novel treatment planning technique to facilitate safe pancreatic SBRT dose escalation.

Pancreatic stereotactic body radiation therapy (SBRT) has emerged as a promising improvement to the radiation component of trimodality therapy for pancreatic adenocarcinoma. Recent data show dramatic clinical outcome improvements for patients treated with dose escalated SBRT. However, the sensitivity and proximity of organs-at-risk (OARs) such as duodenum, stomach, and small bowel pose a considerable challenge to escalation of prescription dose necessary for adequate tumo control. In our study, we identified patients treated on our institutional pancreatic SBRT protocol to 33Gy/5x, and replanned each case with non-coplanar arcs to maximal studied doses, and assessed OAR tolerance.

Methods and Materials:

12 patients were treated under institutional protocol with respiratory gated, triggered kV imaging, axial-arc VMAT plans (2-3 arcs) on a Varian Edge linac, with 10MV FFF beam. Plans were optimized in Eclipse TPS. Each patient’s treatment was re-planned with the addition of two non-coplanar arcs, at 10° and 350° couch kicks, to the axial arc. To isolate the impact of the non-coplanar beam arrangements on plan quality, the plans were optimized congruently with the clinical plans and utilized identical dose constraints. If PTV coverage of re-optimized plan was less than its clinical counterpart, the replan was normalized to identical PTV coverage percentage. Dosimetric quantities compared were: D[0.1cc] to duodenum, small bowel, and stomach; PTV and GTV prescription dose coverage and mean dose.

Each re-plan was exported to Mobius 3D which validated delivery of the plan with respect to gantry/patient/table clearance .

Results:

All non-coplanar arc replans met previously utilized clinical constraints. Mobius 3D verified each plan as deliverable with respect to patient/gantry/table clearance. The addition of non-coplanar arcs improved plan quality in every single re-planned case at no dosimetric expense. Median duodenum, stomach, and small bowel D0.1cc reductions were 203.1cGy, 166.2cGy, and 149.5cGy. PTV and GTV coverage was equivalent or improved in all of the non-coplanar arc plans as well.

Conclusion:

The incorporation of non-coplanar arcs is a simple and effective method to reduce OAR dose exposure in pancreatic SBRT planning. Such techniques become increasingly important as efforts to further dose escalate pancreatic SBRT treatments become more commonplace.

Evan THOMAS (BIRMINGHAM, USA), Christina BLALOCK, Rex CARDAN, Richard POPPLE, Rojymon JACOB
11:39 - 11:45 #17851 - c34-7 Stereotactic body radiation therapy in the management of oligometastatic colorectal cancer.
c34-7 Stereotactic body radiation therapy in the management of oligometastatic colorectal cancer.

Background: The prolongation of survival of metastatic colorectal cancer (CRC) patients with the introduction of new systemic treatments increased the relevance of local approaches in oligometastatic setting. Aim of the present study was to analyze pattern of care and recurrence of oligometastatic CRC patients, and to evaluate predictive factors of survival.

Materials and methods: We included patients with histologically confirmed colorectal adenocarcinoma and maximum of 5 metastases. Previous or concomitant systemic treatments were allowedEnd points of the present study were the outcome in terms of Local control of treated metastases (LC), progression free survival (PFS), and overall survival (OS).

Results: 270 patients were treated on 437 metastases. Characteristics are summarized in Table 1. Lung was site of metastases in 48.5% of cases, followed by liver (36.4%) and lymph nodes (12.4%). Systemic treatment was administered before SBRT in 199 patients (73.7%). Median follow-up time was 22.6 months (3- 98.7). Rates of LC at 1, 3 and 5 years were 95%, 73% and 73%, respectively. Time from diagnosis of metastases to SBRT was the only factor predictive of LC (HR 1.62, p=0.023). Median PFS was 8.6 months and both control of treated metastases (HR 1.86, p=0.000) and single line of systemic treatment before SBRT (HR 1.86, p=0.000) were positively correlated to PFS.  Rates of OS at 1, 3 and 5 years were 88.5%, 56.6%, and 37.2%, respectively. Lesion greater than 30 mm (HR 1.82, p=0.030), presence of metastases in organ different from lung ((HR 1.67, p=0.020), the use of systemic treatment before SBRT (HR 1.82, p=0.023), and progression of treated metastases (HR 1.80, p=0.007), were all predictive of worse OS (Figure 1).

Conclusions: Stereotactic body radiation therapy represents an effective approach in the management of oligometastatic CRC. Control of treated metastases was a strong positive predictive factor for both PFS and OS.

Ciro FRANZESE (Milano, ITALY), Tiziana COMITO, Davide FRANCESCHINI, Elena CLERICI, Fiorenza DE ROSE, Angelo TOZZI, Pierina NAVARRIA, Pietro MANCOSU, Stefano TOMATIS, Marta SCORSETTI
El Pardo I
11:15

Tuesday 11 June

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A35
11:15 - 11:45

PARALLEL SESSION
EVOLUTION AND IMPACT OF RADIOSURGERY

Moderators: Laura FARISELLI (director) (milano, ITALY), Christer LINDQUIST (Medical co-director) (LONDON, SWEDEN), Paul W. SPERDUTO (2HBK7YS$) (Minneapolis, USA)
11:15 - 11:30 What I Know Now That I Wish I Knew Then. Antonio DE SALLES (Professor - Chief) (Sao Paulo, BRAZIL)
11:30 - 11:45 How Radiosurgery has Impacted Radiation Oncology. Scott SOLTYS (ISRS 2019) (Stanford, CA, USA)
Segovia II-III-IV
11:45

Tuesday 11 June

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A36
11:45 - 12:30

PARALLEL SESSION
CONTEMPORARY MANAGEMENT OF BRAIN METASTASES

Moderators: Pablo CASTRO PENA (Radiation Oncologist) (Cordoba, ARGENTINA), Marcos MALDAUN (Neurosurgical Oncology) (São Paulo, BRAZIL), Scott SOLTYS (ISRS 2019) (Stanford, CA, USA)
11:45 - 12:00 #17647 - a36-1 Single versus multifraction stereotactic radiosurgery for large brain metastases: An international meta-analysis of 24 trials.
a36-1 Single versus multifraction stereotactic radiosurgery for large brain metastases: An international meta-analysis of 24 trials.

Purpose: Multifraction stereotactic radiosurgery (MF-SRS) purportedly reduces radionecrosis risk over single fraction SRS (SF-SRS) in the treatment of large brain metastases. The purpose of the current work is to compare local control (LC) and radionecrosis rates of SF-SRS and MF-SRS in the definitive (SF-SRSD and MF-SRSD) and postoperative (SF-SRSP and MF-SRSP) settings.

Methods/Materials: PICOS/PRISMA/MOOSE guidelines were used to select articles where patients: diagnosed with “large” brain metastases (Group A: 4-14 cm3, or about 2-3 cm; Group B:  >14 cm3, or > 3 cm); 1-year LC and/or rates of radionecrosis were reported; radiosurgery was administered definitively or postoperatively. Random effects meta-analyses using fractionation scheme and size as covariates were conducted. Meta-regression and Wald-type tests were used to determine the effect of increasing tumor size and fractionation on the summary estimate, where the null hypothesis was rejected for p<0.05.

Results: Twenty-four studies were included, published between 2008-2017 with 1,887 brain metastases. Local control at 1-year for Group A/SF-SRSD was 77.6% and for Group A/MF-SRSD was 92.9% (p=0.18). Local control at 1-year for Group B/SF-SRSD was 77.1% and for Group B/MF-SRSD was 79.2% (p=0.76). Local control at 1-year for Group B/SF-SRSP was 62.4% and for Group B/MF-SRSP was 85.7% (p=0.13). Radionecrosis incidence for Group A/SF-SRSD was 23.1% and for Group A/MF-SRSD was 7.3% (p=0.003). Radionecrosis incidence for Group B/SF-SRSD was 11.7% and for Group B/MF-SRSD was 6.5% (p=0.29). Radionecrosis incidence for Group B/SF-SRSP was 7.3% and for Group B/MF-SRSP was 7.5% (p=0.85). 

Conclusion: Treatment for large brain metastases with MF-SRS regimens may offer enhanced efficacy and safety when compared to SF-SRS, particularly for tumors 4-14 cm3 (2-3 cm in diameter) treated in the definitive setting. These findings are hypothesis-generating and require validation by ongoing and planned prospective randomized control trials.

Eric LEHRER, Jennifer PETERSON, Nicholas ZAORSKY, Paul BROWN, Arjun SAHGAL, Veronica CHIANG, Samuel CHAO, Jason SHEEHAN, Daniel TRIFILETTI (Jacksonville, USA)
12:00 - 12:15 Japanese Study Group Update: Evidence from “crazy treatment” to standard treatment. Yoshiaysu IWAI (Neurosurgery, Radiosurgery) (Osaka, JAPAN)
12:15 - 12:30 Pre-operative SRS for Brain Metastases : A New Paradigm. Stuart BURRI (Chairman) (Charlotte, USA)
11:45 - 12:30 Current status of pronostic models and grading systems. Paul W. SPERDUTO (2HBK7YS$) (Minneapolis, USA)
Segovia II-III-IV

Tuesday 11 June

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B36
11:45 - 12:45

Oral Session
FUNCTIONAL #2 - MOVEMENT DISORDERS

Moderators: Manoel JACOBSEN TEIXEIRA (BRAZIL), Christer LINDQUIST (Medical co-director) (LONDON, SWEDEN), Alessandra MOURA LIMA (BRAZIL)
11:45 - 11:55 #17895 - b36-1 Probabilistic tractography for radiosurgical dosimetry of functional regions of the thalamus.
b36-1 Probabilistic tractography for radiosurgical dosimetry of functional regions of the thalamus.

RAD-1601 is a clinical trial to determine the efficacy of multileaf collimator based radiosurgical thalamotomy for essential tremor. Because the target location cannot be visualized using conventional MR sequences, it was determined using atlas-based stereotactic coordinates. The isocenter was adjusted to limit the maximum dose in the internal capsule to 26 Gy (20%). The stereotactic coordinates, isocenter, and creation of the treatment plan were automated using scripting of the treatment planning system. The prescription was 130 Gy maximum dose. Prior to treatment, diffusion MR imaging was obtained and used for single-subject thalamic segmentation based on probabilistic tractography (PT). Two relevant regions-of-interest (ROIs) were identified based on the PT results: the region most connected to primary motor cortex (M1), presumed to mirror the histologic ventral intermediate nucleus (VIM), and the region most connected to the supplementary motor area/premotor cortex (SMA/PMC), presumed to mirror the histologic ventral oral nucleus (VO). The corresponding ROIs were imported into the treatment planning system. Segmentation has been obtained for 4 patients. The volumes of M1 and SMA/PMC were 0.1-0.5 cm3 and 0.4-1.1 cm3, respectively. In all 4 cases, both the target based on stereotactic coordinates and the isocenter were located within the SMA/PMC rather than M1. The D0.03cc[Gy] was 81-91 Gy for SMA/PMC and 29.9-48.3 Gy for M1. The maximum dose was 130 Gy for SMA/PMC and 94.7-109.1 Gy for M1. Thalamic segmentation based on probabilistic tractography is a promising technique that may enhance traditional functional SRS targeting. In the future, prospective use of structural connectivity imaging data will result in more functionally relevant targeting for SRS thalamotomy. Correlation of outcome with radiation dosimetry to M1 and SMA/PMC are ongoing.

Richard A. POPPLE (Birmingham, USA), Erik H. MIDDLEBROOKS, Evan M. THOMAS, John B. FIVEASH, Rex A. CARDAN, Harrison C. WALKER, Barton L. GUTHRIE, Markus BREDEL
11:55 - 12:05 #17905 - b36-2 Preliminary results of phase II clinical trial for linac-based coneless and frameless SRS thalamotomy for essential tremor and tremor-dominant Parkinson's disease.
b36-2 Preliminary results of phase II clinical trial for linac-based coneless and frameless SRS thalamotomy for essential tremor and tremor-dominant Parkinson's disease.

Introduction:

Radiosurgery (SRS) has been used to manage tremor in patients with medically refractory tremor. Because of high doses, small target, and required precision, Gamma Knife has been the traditional platform. Our objective was to develop and evaluate a safe, effective, and precise alternative on the linear accelerator without frame or cone. We present here a pre-clinical evaluation of the technique, pilot treatment, and early results of recently-opened phase II evaluation trial of this technique for non-DBS candidate patients.

Methods

Patients’ pre-treatment tremor was evaluated with FTM score and PROMIS index. Patients were imaged on a Phillips 3T Magnetom Prisma MRI with additional optional Siemens 7T Magnetom MR imaging, to generate MPRAGE, diffusion-weighted tractographic, and resting-state fMRI sequences. VIM was identified via thalamic parcellation and compared to stereotactic reference location. Scan was fused to  thin-slice CT simulation obtained with patient immobilized in Qfix Encompass rigid mask. VIM was targeted to 130Gy dmax. SRS was delivered on Varian Edge linac with high-definition multi-leaf collimator (HDMLC) and intrafraction optical surface monitoring (OSMS) to ensure patient stationariness. Treatment was delivered in 13 flattening-filter free non-coplanar arcs with fixed-MLC position and pre-determined beam modulation (Virtual Cone), resulting in spherical dose equivalent to 4mm Gamma Knife shot. Post-treatment imaging and FTM/PROMIS scores were compared to pre-treatment baselines at scheduled intervals.

Results

In the study, 12 patients underwent VIM thalamotomy. QA revealed treatment accuracy to 0.3mm. Median follow-up was 4 months. All patients demonstrated T1-enhancing lesion at site of treatment. All patients had some degree of tremor improvement in limb contralateral to treatment site, ranging from near complete to modest tremor relief. No patient experienced grade 2 or greater treatment-related adverse effect. Additional follow-up continues.

Conclusion

Functional radiosurgery can now be delivered with equivalent dosimetry in comparison to Gamma Knife plans. Treatments on a coneless, frameless linac platform are fast and well tolerated, but as with all functional SRS, require collaborative expertise from an experience functional neurosurgeon, CNS radiation oncologist, and physicist comfortable with small target, high dose QA.

Evan THOMAS (BIRMINGHAM, USA), Richard POPPLE, John FIVEASH, Barton GUTHRIE, Markus BREDEL
12:05 - 12:15 #17661 - b36-3 Ventro-lateral motor thalamus abnormal functional connectivity before and after left Vim radiosurgery for drug-resistant essential tremor: a resting-state fMRI study.
b36-3 Ventro-lateral motor thalamus abnormal functional connectivity before and after left Vim radiosurgery for drug-resistant essential tremor: a resting-state fMRI study.

Background:Essential tremor (ET) is a common movement disorder. Resting state fMRI (rs-fMRI) is a non-invasive neuroimaging method acquired in absence of any task. 

Objective: The first aim of the present study was to correlate pretherapeutic ventro-lateral thalamus functional connectivity (FC) with clinical result 1 year after Vim radiosurgery (Vim RS) for drug-resistant ET. The second aim was to evaluate blood-oxygen level dependent (BOLD) changes between pre- and postherapeutic state. 

Methods: Resting-state was acquired for 17 consecutive (right handed) patients, before and after left unilateral Vim RS. Tremor network was investigated using region-of-interest (ROI), left ventro-lateral ventral (VLV, Morel’s nomenclature) cluster, obtained using automated segmentation from pretherapeutic diffusion MRI. Seed-based functional connectivity (FC) was assessed as correlations between the VLV’s time courses and the one of every voxel. One-year MR-signature volume was always located inside VLV and did not correlate with any reported seed-FC measures (p>0.05). 

Results: We report statistically significant correlations betweenpretherapeutic seed-FC with 1 year clinical outcome for: 1). right visual association area (Brodmann area, BA 19) predicting 1 year activities of daily living (ADL) drop (punc=0.02); 2). left fusiform gyrus (BA 37) predicting 1 year head tremor score improvement (punc=0.04); 3). posterior cingulate (left BA 23, puncor=0.009), lateral temporal cortex (right BA 21, punc=0.02) predicting time to tremor arrest . Longitudinal study displayed changes within right dorsal attention (frontal eye-fields and posterior parietal) and salience (anterior insula) networks, as well as areas involved in hand movement planning or language production. 

Conclusions: Our results suggest that pretherapeutic resting-state seed-FC of left VLV predicts tremor and time to tremor arrest after Vim RS for ET. Visual areas are identified as the main regions in this correlation. Longitudinal changes display reorganization of dorsal attention and salience networks after Vim RS. Beside attentional gateway, they are also known for their major role in facilitating a rapid access to the motor system.

Constantin TULEASCA (Lausanne, SWITZERLAND), Jean RÉGIS, Elena NAJDENOVSKA, Tatiana WITJAS, Nadine GIRARD, Mohamed FAOUZI, Vincent MARION, Jean-Philippe THIRAN, Meritxell BACH CUADRA, Marc LEVIVIER, Dimitri VAN DE VILLE
12:15 - 12:25 #17868 - b36-4 Radiosurgical Pallidotomy for Generalised & Focal Dystonias: Is It The Last Part in The Ship of Theseus.
b36-4 Radiosurgical Pallidotomy for Generalised & Focal Dystonias: Is It The Last Part in The Ship of Theseus.

Objective 

To evaluate the role of radiosurgical pallidotomy in cases of medically refractory generalised and focal dystonias in current era.

Introduction

Gamma knife radiosurgery has been proved to be effective in the management of medically refractory dystonia. Technically, it is considered inferior to deep brain stimulation on the virtue of absence of real time monitoring, latency period for effective results, and irreversible nature of lesioning [1]. We present our experience with five cases of generalised dystonia managed with radiosurgery ablation of the globus pallidus interna. 

Material and Methods

5 patients were treated with Leksell Perfexion gamma knife radiosurgery. 3/5 patients were primary dystonia, while one was suffering from neuroacanthosis, and another developed post traumatic dystonia. Radiosurgical pallidotomy was performed. The target was localised on magnetic resonance imaging after fusion with anatomical atlas. A single shot of 4 mm collimator was used with 140 Gy marginal dose at prescription iso dose of 100% [1,2]. Peri procedure steroids were administered.

Results

The median time to improvement was 70 days. Complete abolition of movement was observed in 20% of patients, while excellent relief in 40%. New onset deficit was observed in 2/5 (40%) patients. One patient developed bilateral homonymous hemianopia within one week of GKRS. Another patient developed hemiparesis after 4 months of radiosurgery due to development of infarct in the posterior limb of internal capsule. One patient developed steroid resistant brain edema which needed Bevacizumab for the management. Follow up radiology at three months resulted in 4-5 mm well circumscribed lesion with peripheral contrast enhancement surrounding a low signal region. 

Conclusion

Radiosurgical pallidotomy is not a shot in the dark. It should still be considered a treatment modality for selected cases of dystonia. It remains an attractive option in patients with advanced age, significant medical comorbidities, that forbid open stereotactic procedures, or patients on anticoagulation therapy. In resource stricken countries such as India, where majority of the population remains noninsured, lesion intervention is a more feasible option. 

Manjul TRIPATHI (Chandigarh, INDIA)
12:25 - 12:35 #17485 - b36-5 VIM Radiosurgery for tremor : results of a large prospective cohort of 626 consecutive patients.
b36-5 VIM Radiosurgery for tremor : results of a large prospective cohort of 626 consecutive patients.

Objective : Gamma Knife Radiosurgery (GKS) is one of the neurosurgical technics available for the management for severe drug resistant tremor. We are evaluating hereafter safety efficacy of GKS based on the prospective assessment of one of the larger cohort worldwide.

 Materiel & Method :  Between January 2004 & November 2018, 626 patients have been operated using GKS in Timone Marseille University by a single Neurosurgeon (JR). The tremor was an essential tremor (ET) in 432 patients, a parkinsonian one in 88, a mixt in 42, a multiple sclerosis in 8 and other in 11. GKS was performed on the left VIM in 81% of the patients who were males in 58,6% of the cases. The mean age was 73 years (min 31- max 93). Tremor, neuropsychological exam, speech, gait and balance were all assess before and 1 year after.

 Results : The mean follow up is 18 months. In 30 patients (4,7%) we were unable to achieve sufficient FU by ourselves and the FU was performed by the local neurologists of the patients or lost for FU. The mean delay of action of radiosurgery was 4,5 months. The mean disability was before GKS of 30,2/75 and at the last FU of 8,9/75 for a mean improvement of 70,5%. The amplitude of the hand tremor on the treated side was in mean before GKS of 18,7 and at the last FU of 6,6 for a mean improvement of 64,7%. The functional impact was in mean before GKS of 7,66/28 and at the last FU of 2,48/28 for a mean improvement of 67,6 %. An hyper-response to radiosurgery associated to clinical side effects (proprioceptive ataxia, dysarthria, hemiparesis) was observed in 77% of the patients and led to rehabilitation (+- Avastin or hyperbaric oxygen).

 Conclusion : It may be the largest series of GKS for tremor, with a strict prospective assessment. Results are demonstrating the high safety efficacy ratio of this approach in this population of aged and fragile patients. 

Jean REGIS, Giorgio SPATOLA, Axel CRETOL (Marseille), Tatiana WITJAS
12:35 - 12:45 #17836 - b36-6 Gamma Forel's campotomy for dystonia with coarse tremor.
b36-6 Gamma Forel's campotomy for dystonia with coarse tremor.

Introduction: Multiple therapies exist for dystonia, however refractory forms are still challenging. In 1963, Spiegel reported stereotaxic radiofrequency Forel’s Campotomy (FC) to treat Parkinson's disease symptoms. The interruption of the fibers at this target improved dystonia and tremor. It also improved rigidity and tremor in patients with Parkinson’s disease.

Objective To show a Gamma Knife Radiosurgery (GKR) Forel's campotomy to treat dystonia levodopa-responsive with coarse tremor component using the GK Perfexion model (Elekta AB).

Methods: A 29-year-old-woman with a history of neuropsychomotor developmental delay presented generalized dystonia and bilateral proximal tremor of great amplitude since childhood. Magnetic resonance was unremarkable. The dystonia improved significantly with levodopa. She increased dosage over the years up to 1200mg/day and finally lost control of the movement disorder. The most limiting symptom was the coarse proximal tremor in the superior limbs. The patient is right handed. Bilateral deep brain stimulation was offered but declined by the family. GKR was indicated to improve control of the tremor and the dystonia. The left pallido-thalamic tract received 140Gy at the 100% point, using two 4mm collimators. Final targeting was defined using fiber tracking, with attention to the internal capsule dose constrains. Stereotactic coordinates in relation to AC-PC line for the first collimator were x=9mm to the left,  y= at MCP, z= 1mm above, while for the second collimator were x= 10mm left, y= 1mm posterior to MCP, z=1mm above. Treatment lasted 126 minutes. The patient was discharged on the same day. Progressive improvement was noticed at 2 months post-treatment with the patient initiating self-care tasks.

Conclusion: Gamma Knife Forel’s Campotomy for tremor associated with dystonia is feasible. The literature on ablative procedure at Forel’s field is very scarce. Larger number of cases and longer follow-up are needed to validate this approach. 

Juliete MELO DINIZ (SAO PAULO, BRAZIL), Antônio DE SALLES, Rafael COSTA LIMA MAIA, Aline Lariessy CAMPOS PAIVA, Crystian WILIAN CHAGAS SARAIVA, Alessandra GORGULHO
Segovia I

Tuesday 11 June

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C36
11:45 - 12:45

Oral Session
VASCULAR DISORDERS

Moderators: Marcello REIS DA SILVA (Neurosurgeon) (RIO DE JANEIRO, BRAZIL), Vladimir ZACCARIOTTI (Neurosurgeon in Chief) (Goiania, BRAZIL)
11:45 - 11:55 #17638 - c36-1 Safety-efficacy of stereotactic radiosurgery in the treatment of ARUBA-eligible patients with unruptured brain AVM ⩽ 5 cc: a cohort of 247 patients.
c36-1 Safety-efficacy of stereotactic radiosurgery in the treatment of ARUBA-eligible patients with unruptured brain AVM ⩽ 5 cc: a cohort of 247 patients.

ObjectiveAccording to ARUBA’s trial conservative treatment seems to be superior to any intervention for unruptured brain arteriovenous malformations (AVM). The aim of this study is to evaluate if this cohort of ARUBA-eligible AVM with a volume ⩽5cc treated by SRS are in line with ARUBA trial. 

 

Materials and methods:A retrospective study was conducted to evaluate the middle and long-term outcomes of unruptured naive brain AVM with a volume ⩽5cc eligible to ARUBA study treated by Gamma-Knife (GKRS) and followed at least 3 years.

 

Results:

From 1992 to 2014, 1979 patients were treated by GKRS for AVM in the Timone University Hospital, among them 249 patients were included in this study. The median age was 36 years (range 18-78). The median treated volume of the nidus was 1.3 cc (range 0.4-5) and 63% of the AVM were in eloquent areas (n=157). In most of the AVM, the RBAS was 1-1.8 (76%) (n=190), the Spetzler-Martin grade was II-III (73%) (n=180), and the VBAS was ≤1point (75%) (n=187).

The overall AVM obliteration rate was 77.1% after at least 3 GKRS session. The obliteration rate was 67% and 73.5% after 1 or 2 GKRS session. The average dose at the margin was 24 Gy (range 15-25) and the median follow-up was 45.04 months (range 36–205.28). Eight patients (3.2%) experienced a hemorrhage after GKRS session, corresponding to a post-GKRS hemorrhage rate of 1.03% per year. The permanent symptomatic RIC rate was 2% (n=5), among them 4 patients (4.7%) increased seizure, 1 with neurological deficit (2.1%). No patient presented radionecrosis or cyst were at last follow-up. 

Conclusion: Our results are not confirming ARUBA conclusions for this AVM cohort ⩽5 cc. The very low toxicity rate with the high occlusion rate is preaching in favor of upfront GKRS for naive unruptured small AVM.

Jean REGIS (Marseille), Jean-François HAK, Giorgio SPATOLA
11:55 - 12:05 #17886 - c36-2 IntuitivePlan inverse planning performance evaluation for arteriovenous malformations.
c36-2 IntuitivePlan inverse planning performance evaluation for arteriovenous malformations.

Forward dose planning for Gamma Knife radiosurgery (GKRS) can be a challenging task and typically requires substantial planning experience to produce optimal clinical plans. IntuitivePlan offers an inverse planning software solution based on convex optimization. It allows additional user interactivity for fine tuning, which has the potential to improve the treatment planning process in terms of quality and efficiency.

In this study we aim to prospectively compare the performance of this novel software solution against manual plans performed by an expert user. A total of 20 arteriovenous malformation (AVM) cases were included in this study, and competing inverse plans were compared using various plan parameters including: Coverage, selectivity, Gradient Index, Paddick Conformity Index, Efficiency Index, beam-on time, number of shots and total planning time

Initial results show that IntuitivePlan produces plans of comparable plan quality for a range of AVM shapes and volumes. Despite the use of substantially more shots that are not “classical”, IntuitivePlan produces dosimetric indices comparable to an expert planner in less than 8 minutes.

Ian PADDICK (Streatley, UK), Alexis DIMITRIADIS
12:05 - 12:15 #17021 - c36-3 Intracranial Dural Arteriovenous Fistulas with Cortical Venous Drainage: Gamma Knife Radiosurgery as the Treatment of Choice.
c36-3 Intracranial Dural Arteriovenous Fistulas with Cortical Venous Drainage: Gamma Knife Radiosurgery as the Treatment of Choice.

Objective: To evaluate the clinical and radiological outcome of Gamma knife radiosurgery (GKS) in the treatment of intracranial dural arteriovenous fistula (DAVF) with cortical venous drainage (CVD) and compare it with the outcome of endovascular therapy.

Methods: This series includes patients who underwent GKS or endovascular therapy for intracranial DAVF with CVD over 10 years (Jan 2007 to Dec 2016) at the All India Institute of Medical Sciences, New Delhi. Their demographic profile, clinical presentation, imaging details, and follow up clinical status were reviewed retrospectively. Clinical follow up was done once in every 6 months. Radiological follow up using digital subtraction angiography (DSA) was performed at a mean duration of 24 months post intervention. Patients who had a clinical follow up of less than 1 year were excluded from the study.

Results: 35 patients (26 in embolization group and 9 in GKS group) who had intracranial DAVF with CVD were included the study. Clinical improvement was seen in 77.78% of the patients who received GKS and 57.7% in the patients who underwent embolization (p = 0.431). Complete obliteration of DAVF was seen in 55.56% of the patients in the GKS group and 57.7% of the patients in the embolization group (p = 1).

Conclusion: Our study shows that GKS is at least as effective as embolization in terms of clinical and radiological outcome in the treatment of intracranial DAVF with CVD. Contrary to popular perception, GKS should also be considered as the first line treatment of intracranial DAVF with CVD.

Hardik SARDANA (New Delhi, INDIA), Deepak AGRAWAL
12:15 - 12:25 #16718 - c36-4 Dose Response in Volume Staged Radiosurgery for Large Arteriovenous Malformations: A Multi-Institutional Study.
c36-4 Dose Response in Volume Staged Radiosurgery for Large Arteriovenous Malformations: A Multi-Institutional Study.

Abstract

Background

Optimal treatment paradigm for large arteriovenous malformations (AVMs) is controversial. Volume-staged stereotactic radiosurgery (VS-SRS) provides an effective option for these high-risk lesions, but optimizing treatment for these recalcitrant and rare lesions has proven difficult.

 

Methods

This is a multi-centered retrospective review of patients treated with a planned prospective volume staging approach to stereotactically treat the entire nidus of an AVM with volume stages separated by intervals of 3-6 months. A total of 9 radiosurgical centers treated 257 patients with VS-SRS between 1991 and 2016. We evaluated near complete response (nCR), obliteration, cure, and overall survival.

 

Results

With a median age of 33 years old at the time of first SRS volume stage, patients received 2-4 total volume stages and a median follow up of 5.7 years after VS-SRS. The median total AVM nidus volume was 23.25 cc (range: 7.7-94.4 cc) with a median margin dose per stage of 17 Gy (range: 12-20 Gy). Total AVM volume, margin dose per stage, compact nidus, lack of prior embolization, and lack of thalamic location involvement were all associated with improved outcomes. Dose >/= 17.5 Gy was strongly associated with improved rates of nCR, obliteration, and cure. With dose >/= 17.5 Gy, 5- and 10- year cure rates were 33.7% and 76.8% in evaluable patients compared to 23.7% and 34.7% of patients with 17 Gy  and 6.4% and 20.6% with /= 17 Gy at 5 years (p = 0.007). For compact nidus architecture, the obliteration rates at 5 years were 10.7% vs 9.3% vs 26.6% for dose >17 Gy vs 17 Gy vs >/= 17.5 Gy (p = 0.952).

 

 

Conclusion

VS-SRS is an option for upfront treatment of large AVMs. Higher dose was associated with improved rates of nCR, obliteration, and cure suggesting that larger volumetric responses may facilitate salvage therapy and optimize the chance for cure.

Zachary SEYMOUR (Dearborn, USA), Jason CHAN, Penny SNEED, Hideyuki KANO, Rachel JACOBS, Craig LEHOCKY, L. Dade LUNSFORD, Hong YE, Tomas CHYTKA, Roman LISCAK, Cheng-Chia LEE, Huai-Che YANG, Dale DING, Jason SHEEHAN, Caleb FELICIANO, Rafael RODRIGUEZ-MERCADO, Veronica CHIANG, Judith HESS, Samuel SOMMARUGA, Brendan MCSHANE, John LEE, Anthony KAUFMANN, Inga GRILLS, Micheal MCDERMOTT
12:25 - 12:35 #17861 - c36-5 Long-term results following repeat gamma knife surgery for incompletely obliterated arteriovenous malformations after the first gamma knife treatment.
c36-5 Long-term results following repeat gamma knife surgery for incompletely obliterated arteriovenous malformations after the first gamma knife treatment.

Objective: Gamma Knife Surgery (GKS) may be repeated for incompletely obliterated arteriovenous malformations (AVM) following initial GKS (iGKS). However, reports on the results are sparse. We reviewed our national series of patients.

 

Methods: Of 521 patients treated for AVM with GKS in Norway between 1988 and 2016, 55 (10.6%) (32 males, median age 39 y) received repeat-GKS including 26 (47.3%) unruptured and 7 AVMs (13%) with associated aneurysm. Two (3.6%) AVMs, one with prior hemorrhage and aneurysm, ruptured between treatments, at 5 and 29 months. The mean nidus volume was 1.67 cm³ (range 0.1-6.6) at iGKS and 0.49 cm³ (range 0.1-3.96) at repeat-GKS. The mean volume reduction and time between treatments was 62% (range 0-99.9%) and 44 months (range 5-110), respectively. Mean follow-up after repeat-GKS was 42 months (range 0-69). One patient (2%) refused follow-up.

 

Results: Complete obliteration was achieved in 28 out of 55 repeat-treated AVMs (51%) while 15 (27%) were reduced in size and 11 (20%) unchanged. The median time to obliteration was 57 months (95% CI: 40-74). Out-of-field failure was seen in 29 (52.7%) AVMs following iGKS (reapperance of compressed nidus by hemorrhage (n=2), inadequate angiography (n=5) and incomplete delineation of nidus (n=22)); and 3 (5.5%) following repeat-GKS (inadequate angiography). The risk of bleeding/year was reduced from 2.3% before treatment to 0.8% between treatments and 0% following repeat-GKS. The complication rate for iGKS and repeat-GKS was 9% (n=5); worsening of epilepsy (n=1), cyst formation (n=1) and temporary neurological deficits (n=3). One patient with an obliterated AVM died of an unrelated cause.

 

Conclusion: Our long-term results are encouraging compared to those predicted by the ARUBA trial. Following repeat-GKS the obliteration rate was increased from 0 to more than 50% with a low risk of complications. Of note, the risk of hemorrhage was reduced also for subtotally obliterated AVMs.

Bente Sandvei SKEIE (Paradis, NORWAY), Peter QUARCOO, Jan Ingemann HEGGDAL, Kjersti Gaustad KLETT, Elisabeth LARSEN, Paal-Henning PEDERSEN, Geir Olve SKEIE , Per Øyvind ENGER
12:35 - 12:45 #17875 - c36-6 Stereotactic Diffusion Tensor Tractography For Gamma Knife Stereotactic Treatment Of Brain Arteriovenous Malformations.
c36-6 Stereotactic Diffusion Tensor Tractography For Gamma Knife Stereotactic Treatment Of Brain Arteriovenous Malformations.

Objectives:

Advances in neuro-imaging have improved the safety of stereotactic radiosurgery. Nonetheless GammaKnife radiosurgery for AVM still has a risk of developing new neurological deficits which may be permanent. We report our experience with integrating stereotactic diffusion tensor imaging (DTI) tractography into treatment planning for Gamma Knife radio-surgery for Arteriovenous Malformations

Methods:

40 Day of treatment  Stereotactic DTI studies were performed in 37 patients who underwent GKRS for AVM. Marginal dose 18-25 Gy. 3 patients underwent staged SRS of large AVM & five patients were had previous GK for their AVM. DTI images were obtained at the time of standard GKRS protocol MRI (T1 and T2 weighted) for treatment, with the patient's head secured by a Leksell stereotactic frame. DTI was performed with diffusion gradients in 32 directions and coregistered with the volumetric T1-weighted study. DTI post-processing by means of commercially available software allowed tensor computation and the creation of directionally encoded color, apparent diffusion coefficient & fractional anisotropy mapped sequences. In addition, the software allowed visualized critical tracts to be exported as a structural volume and integrated into GammaPlan as an “organ at risk” during shot planning.Tracts at risk were subjected to dosimetry. Patient follow-up was 3 months to 3 1/2 years with 26 patients returning for post teatment DTI.

Results:

DTI allowed visualisation & dosimetry of eloquent white fibre tracts (optic radiation, corticospinal tract & arcuate fasiculus) during treatment planning.

Most patients had pathology in the vicinity of eloquent tracts and/or the cortex. One patient with mesial temporal AVM developed delayed worsening of a pre-existing hemianopia & another with AVM required steroids for cerebral swelling. no other neurological deficits due to radiation were recorded at follow-up.  

Conclusions:

Tractography has been reported to reduce the risk of motor complcations after SRS for AVM.iStereotactic Tractography represents a promising tool for preventing GK-SRS complications by reduction in radiation doses to functional organs at risk, including critical cortical areas and subcortical white matter tracts & further increase our knowledge of critical cerebral structure radiation tolerances to better improve the therapeutic potential and safety of SRS for AVMs

Cormac GAVIN (London, UK), H. Ian SABIN
El Pardo I
12:45

Tuesday 11 June

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A37
12:45 - 13:45

ISRS BOARD MEETING
for Board of Directors only

Oriente
14:00

Tuesday 11 June

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C37
14:00 - 15:30

Session Ibero-Latin-American Society of Radiosurgery
Part I

Moderators: Julio ANTICO (ARGENTINA), Sergio MORENO-JIMENEZ (Chief) (Mexico city, MEXICO), Kita SALLABANDA (Asoc.Prof.) (Madrid, SPAIN)
14:00 - 14:10 Advances in the Treatment of Giant Metastases: Surgery versus Staged Radiosurgery. Eduardo LOVO IGLESIAS (Brain and Spine Radiosurgery Program) (San Salvador, EL SALVADOR)
14:10 - 14:20 Radiosurgery as a Rescue Treatment for High Grade Glioma: Does it Work and Controversies. Pablo CASTRO PENA (Radiation Oncologist) (Cordoba, ARGENTINA)
14:20 - 14:30 Advances on the Treatment of Spine Metastases: Radiosurgery versus Conventional Radiotherapy. Lucas Ignacio CAUSSA (MD) (Córdoba, ARGENTINA)
14:30 - 14:40 Radiosurgery in the Treatment of Multiple Metastases: The Importance of Global Volume. Christian VARGAS (PERU)
14:40 - 14:50 Radiosurgery and Epilepsy. Sergio MORENO-JIMENEZ (Chief) (Mexico city, MEXICO)
14:50 - 15:00 Radiosurgery in Giant AVMs: Which is the Best Option? Kita SALLABANDA (Asoc.Prof.) (Madrid, SPAIN)
15:00 - 15:10 Treatment of Cranial Base Tumors: When Radiosurgery? Alessandra GORGULHO (Director of Research Affairs) (Sao Paulo, BRAZIL)
15:10 - 15:30 Discussion.
El Pardo I
15:30 COFFEE BREAK - POSTERS & EXHIBITION
16:00

Tuesday 11 June

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C38
16:00 - 18:00

Session Ibero-Latin-American Society of Radiosurgery
Part II

Speakers: Miguel A. CELIS (DIRECTOR) (MEXICO, MEXICO), Sergio MORENO-JIMENEZ (Chief) (Mexico city, MEXICO), Kita SALLABANDA (Asoc.Prof.) (Madrid, SPAIN)
16:00 - 16:10 Radiosurgery Concepts, Devices, Penumbra and Precision QA. Daniel VENENCIA (ARGENTINA)
16:10 - 16:20 Certification Program in Radiosurgery: Requirements. J. Miguel DELGADO (MEXICO)
16:20 - 16:30 Radiosurgery in Large Lesions: Hypofractionation, Advantages and Controversies. Rafael GARCÍA DE SOLA (Madrid, SPAIN)
16:30 - 16:40 Radiosurgery in Pediatric Patients: Specific Concepts. Carlos CHIRAOLA (ARGENTINA)
16:40 - 16:50 Combined Treatment in Large Schwannomas. Jose LORENZONI (CHILE)
16:50 - 17:00 Radiosurgery in Acoustic Schwannomas. Jorge MANDOLESI (Neurosurgeon) (BUENOS AIRES, ARGENTINA)
17:00 - 17:10 Long Term Follow up of SRS for Radiosurgery. Julio ANTICO (ARGENTINA)
17:10 - 17:20 SRS for Deep Cavernomas. Jessica CHAVEZ NOGUEDA (Radiation Oncologist) (México, MEXICO)
17:20 - 17:30 SRS for Glomus Tumors. Ascary VELAZQUEZ-PACHECO (Professor / Medical Staff) (Monterrey, MEXICO)
17:30 - 17:40 SRS for Choroidal Melanomas. Luis LARREA (Director) (Valencia, SPAIN)
17:40 - 18:00 Discussion.
El Pardo I