ESTRO 37 Abstract book

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ESTRO 37

median. Patients were treated with concomitant temozolomide chemotherapy in 9 cases and with concomitant bevacizumab therapy in one case. The number of foci ranged from 2 to 5 with a median number of 3. Median volumes of GTVs were 37.4 (n=12), 2.9 (n=7), 0.7 (n=6), 0.2 (n=4) and 0.15 cc (n=3). Median volume of the PTV was 475.8 cc and the median PTV to brain ratio 35 percent. Median D2% was 60.6 Gy, median V30Gy of the brain was 64.9% and median V45Gy of the brain 44.3%. Median overall survival was 6 months (95%-KI 4.6 – 7.4 months) and median progression free survival 5 months (95%-KI 4.0 – 6.0 months). On Kaplan-Meier estimators median overall survival and progression-free survival was different between patients with up to 3 foci and for patients with more than 3 foci (8 vs. 4 months, p=0.237; 5 vs. 3 months, p=0.068). Conclusion In patients with multifocal glioma overall and progression-free survival is limited despite aggressive primary treatment. The number of foci seems to be related to radiation treatment outcome with prolonged overall and progression-free survival in patients with up to 3 foci. Further investigations are necessary to optimize treatment for multifocal glioma patients to improve survival after radiation therapy. EP-1209 Long-term outcomes following conventionally fractionated stereotactic boost for high-grade glioma M. Repka 1 , S. Lei 1 , L. Campbell 1 , S. Suy 1 , J. Voyadzis 2 , C. Kalhorn 2 , K. McGrail 2 , D. Subramaniam 3 , S. Collins 1 , W. Jean 2 , B. Collins 1 1 Georgetown University Hospital, Radiation Medicine, Washington, USA 2 Georgetown University Hospital, Neurosurgery, Washington, USA 3 Georgetown University Hospital, Medical Oncology, Washington, USA Purpose or Objective High-grade glioma is the most common primary malignant tumor of the CNS, with death often resulting from uncontrollable intracranial disease. Radiation dose may be limited by the tolerance of critical structures, such as the brainstem and optic apparatus. In this report, long- term outcomes in patients treated with conventionally fractionated stereotactic boost for tumors in close proximity to critical structures are presented. Material and Methods Patients eligible for study inclusion had a pathologically confirmed high-grade glioma status post surgical resection. Inclusion criteria required tumor location within one centimeter of a critical structure, including the optic chiasm, optic nerve, and brainstem. Radiation therapy consisted of 44 to 50.4 Gy, followed by a conventionally fractionated stereotactic boost to a total dose of 54 to 60 Gy. Local failure was scored according to the RANO Criteria. Statistically significant predictors of overall survival and freedom from local progression were identified on univariate analysis, and multivariable analysis was used to confirm these effects. Toxicity was scored according to NCI-CTCAE v3.0. Results Between September 2002 and April 2012, 30 patients eligible for study inclusion underwent resection of a high- grade glioma. The median initial adjuvant EBRT dose was 50 Gy, with a range from 44 Gy to 50.4 Gy. The median conventionally fractionated stereotactic boost 10 Gy, with a range of 10 Gy to 14 Gy. All stereotactic treatments were given in 2 Gy daily fractions. Median follow-up time for the entire cohort was 38 months with a median overall survival of 45 months and five-year overall survival of 32.5%. In patients with WHO Grade III disease, the median overall survival was 61 months, compared to 20 months in patients with glioblastoma ( p < 0.01).The median freedom from local progression was 45

months, and the five-year freedom from local progression was 29.7%. In patients with WHO Grade III disease, the median freedom from local progression was 56 months, compared to 16 months in patients with glioblastoma ( p < 0.01). Multivariable testing confirmed tumor histology to be an independent predictor of overall survival (HR = 0.200, p = 0.002) and freedom from local progression (HR = 0.153, p = 0.002), while extent of resection could not be confirmed as a predictor of either outcome. No patient experienced toxicity attributable to the optic chiasm, optic nerve, or brainstem and no confirmed cases of radionecrosis were identified. Conclusion Oncologic and toxicity outcomes in high-grade glioma patients with tumors in unfavorable locations treated with conventionally fractionated stereotactic boost are comparable to those reported in the literature. This treatment strategy is appropriate for those patients with resected high-grade glioma in close proximity to critical structures. EP-1210 Active beam scanning proton therapy for vestibular schwannomas: early outcomes D. Amelio 1 , D. Scartoni 1 , R. Righetto 1 , L. Widesott 1 , M. Schwarz 1 , M. Amichetti 1 1 Centro di Protonterapia, U.O. Protonterapia- Azienda Provinciale per i Servizi Sanitari - Trento, Trento, Italy Purpose or Objective To report preliminary outcome and toxicity of active beam scanning proton therapy (PT) for vestibular schwannomas (VS). Material and Methods Between October 2014 and June 2017 10 patients (pts) with unilateral VS were treated with PT. Median age was 51 years (range, 43-77) while KPS ranged between 90 and 100 (median 90); two were female (20%), and 8 were male (80%). Diagnosis was based on the typical imaging appearance of VS in all pts. Facial nerve function (House- Brackmann [HB] Grade 1) and trigeminal nerve function were normal in all pts. Two pts (20%) had good or excellent hearing (Gardner-Robertson [GR] Grade 1), and one pt (10%) had serviceable hearing (GR Grade 2). Standard fractionated PT was used at daily dose of 1.8 Gy(relative biologic effectiveness [RBE]); all but one pts received 50.4 GyRBE in 28 fractions. One patient (pt) was treated with PT radiosurgery: 12 GyRBE in one fraction. All pts were treated with active beam scanning PT using 3-4 fields with single field optimization technique. Treatment planning was based on CT and MRI. The gross target volume (GTV) was defined as the area of contrast enhancement on T1-weighted MRI, and the planning target volume (PTV) included a 3 mm safety margin. GTV ranged from 0,2 to 13.3 cc (median 2.4 cc). Toxicity was assessed according to Common Terminology Criteria for Adverse Events version 4.0. Minimum follow-up was 3 months. Median follow-up time was 9 months (range, 3- 36). Results All pts completed the treatment without breaks. Registered acute side effects include grade 1 (10%) fatigue, grade 1 (20%) muffled, grade 2 (20%) headache, grade 2 (10%) nausea. There were no grade 3 or higher acute toxicities. Registered late side effects include grade 1 (10%) and grade 2 (20%) dizziness, grade 2 (10%) vertigo, grade 2 (10%) nausea, facial nerve deficit (HB grade 2) (10%). During follow-up one pt (10%) with the largest VS (13.3 cc) and brainstem compression (Koos 4) developed hydrocephalus that needed ventricul- operitoneal drain; the same patient developed also brainstem radionecrosis (diagnosed at imaging) with facial and trigeminal cranial nerve palsy, gait deficit and imbalance. This pt was treated with steroids and hyperbaric oxygen therapy: after 205 sessions radionecrosis resolved with symptoms improvement.