ESTRO 2020 Abstract book

S519 ESTRO 2020

them after photons (total dose range 16-54 Gy) and one with carbon ions (70,4 GyRBE).Registered side effects were graded according to CTCAE4.0. Results PT was well tolerated,34 pts completed it without breaks related to acute side effects.Two pts interrupted definitively the treatment due to distal disease progression and general conditions decline.A conventional fractionation technique was used for 29 treatments, in 7 cases a Simultaneous Integrated Boost technique was used.All pts were treated with active beam scanning PT. Mean high-risk (HR) PTV volume was 59 cc(range 2.20- 329,4); mean low-risk (LR) PTV volume was 100 cc(range19,35 - 248,08). Mean prescribed total dose was 70 GyRBE (range 54-74 GyRBE) for HR PTV and 54 GyRBE (range 50-60 GyRBE) for LR PTV.Acute Grade (G)3 toxicity was experienced in 3 cases.No other ≥ G3 acute side effects were reported.Acute G2 and G1 toxicity was reported respectively in 22 and 34 cases (table 1).Late Grade 3 toxicities were recorded in 3 pts.Late G2 toxicities and late G1 toxicity was reported respectively in 6 and 19 patients (table 1).At a median follow-up of 18,95 (range 0- 50,70) months, 3 local recurrence were observed between 5.17 and 36.23 months.Of the 27 lesions treated with radical intent, 22 are locally controlled, in 2 cases there was local progression, one pt died during PT for general conditions decline,one pt had distant progression during PT, 2 pts died for the disease.Of the 8 pts treated with adjuvant intent all are free of disease

Purpose or Objective The possibility to combine stereotactic radiotherapy (SRT) of brain metastases (BMs) with systemic treatment remains controversial, especially in terms of potential risk of increased toxicity. Radionecrosis (RN) is the main toxicity induced by SRS of BMs, observed in approximately 15% of BMs. Our study aimed to compare the incidence of RN in patients treated with SRT for BMs with and without concomitant systemic therapy and to evaluate factors influencing survival outcomes in patients with RN. Material and Methods From January 2012 to December 2018, SRT was administrated to 652 patients (p) with a total of 1565 BMs; 430 patients (65.9%) with 1018 of BMs (67.2% of all BMs) were treated with concomitant systemic treatment: 137 patients (21.0%) with immunotherapy (368 BMs, 23.4%), 130 patients (19.9%) with target therapy (TT) (320 BMs, 20.4%) and 163 patients (25.0%) with chemotherapy (330 BMs, 23.2%). In patients with RN, median total dose of 26.6 Gy was administrated (range 15-40Gy), with the most frequent dose schedules of 27Gy/3fr (29 BMs), 30Gy/3fr (28 BMs) and 33Gy/3 fr (23 BMs). All statistical tests were two-sided (p<0.05), Kaplan-Meier’s analysis were used to determine median overall survival (mOS), local and distant progresion free survival (SPSS v.23). Results A total of 147 BMs (9.5%) developed RN after SRS, with no statistically significant difference regarding concomitant therapy in this cohort (p=0.349). In the entire cohort treated with systemic treatment, RN was observed in 9.5% of patients treated with immunotherapy (34p), 10.7% of patients treated with TT (33p) and 7.5% of patients treated with chemotherapy (29p), with no statistically significant differences between groups (p=0.805). Interestingly, mOS of patients with RN was more then double in patients treated with systemic therapy compared with patients not treated (27.5 months vs. 12.5 months, respectively). RN was observed in 60 BMs of NSCLC, 32 of melanoma, 21 of breast, 10 of renal, 8 of colorectal cancer, and 10 BMs with other histologies. Results of mOS (p=0.000), local (p=0.049) and distant control (p=0.035) were statistically different according to the primary tumor histology. Conclusion In our study, neither the concomitant systemic therapy nor the type of systemic drug was associated with higher risk of RN. Moreover, patients with RN showed substantially better mOS in comparison with patients who did not develop RN. In the cohort of BMs with RN, systemic therapy also improved mOS, proving that these combinations were safe and more effective than exclusive SRT. PO-0885 Radiation-induced edema in reirradiation of recurrent high-grade gliomas treated with Proton therapy A. Turkaj 1 , D. Scartoni 1 , I. Giacomelli 1 , P. Feraco 2 , F. Fellin 1 , M. Lipparini 1 , M. Amichetti 1 , D. Amelio 1 1 Centro di Protonterapia, Azienda Provinciale per i Servizi Sanitari Trento, Trento, Italy ; 2 Radiologia Diagnostica- Presidio Ospedaliero Santa Chiara, Azienda Provinciale per I Servizi Sanitari Trento, Trento, Italy Purpose or Objective During and after re-irradiation of relapsed high-grade gliomas (rHGG) variation of edema (ED) is a common event and may translate into neurological symptoms, clinical deterioration and steroid use modification.In magnetic resonance imaging (MRI), ED is usually evaluated with T2 or fluid-attenuated inversion recovery (FLAIR) sequences. Aim of the study was to report a quantitative analysis of radiation-induced ED during and after proton therapy (PT)

Conclusion Our data confirm that PT is an effective treatment for skull base tumors and considering the high doses delivered and the proximity of adjacent critical structures the toxicity late profile is acceptable.A longer follow-up is obviously needed to gain more robust data for late toxicity and long term disease control. PO-0884 Risk of radionecrosis in brain metastases treated with SRT and systemic therapy K. Holub 1,2,3 , G. Louvel 2 1 University of Barcelona- Hospital Clinic de Barcelona, Radiation Oncology, Barcelona, Spain ; 2 Gustave Roussy, Radiation Oncology, Villejuif- Paris, France ; 3 SEOR-CRIS Fundation

re-irradiation of rHGG. Material and Methods

Between January 2015 and September 2019 thirty-nine patients (pts) with rHGG were re-irradiated with PT at our