ESTRO 2020 Abstract Book

S475 ESTRO 2020

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) Between January 2015 and September 2019 thirty-nine patients (pts) with rHGG were re-irradiated with PT at our institution. Twenty seven pts underwent MRI early before, during, at the end as well as 1 month after the treatment and were included in the analysis. All pts received 36 GyRBE in 18 fractions.ED was evaluated and contoured on 108 MRI scans using T2 and FLAIR sequences (5 mm thickness). ED volume (in cc) was quantified as any T2 and FLAIR changes excluding the Gross Tumor Volume. We analyzed the temporal change of ED at the baseline, mid- therapy, at the end, and 1 month after treatment. Mean values of differently delineated ED volumes were compared each other by paired Student’s t-test; p < 0.05 was considered significant. Results Twenty two pts were treated for recurrent glioblastoma and 5 for anaplastic gliomas. Median (Med) CTV was 80 cc (range, 12-259). Med ED volume at the baseline, mid- therapy, at the end, and 1 month after treatment was 62 (range 7-265), 79 (range 9-242),82 (range 10-194),77 cc (range 9-200), respectively. During treatment ED increased in 19 pts (70%) and decreased in 8 (30%). Such increase of ED volume was statistically significant both at mid-therapy and at the end of the treatment with respect to baseline (p=0,004 and 0,01, respectively) but it was associated with mild symptoms only in 10 pts (37%) and was controlled with modification of steroids dose. One month after treatment ED decreased in 11 pts (40%), increased in 10 (37%) and was stable in 6 (22%). As a consequence, mean ED values 1 month after treatment did not significantly differ with respect to baseline. Seven out of 10 pts (70%) with increased ED needed modification of steroids dose. During follow up 3 pts (13%) developed radionecrosis (RN - re-irradiation of rHGG. Material and Methods

diagnosed at imaging) with mild symptoms controlled with steroids. In pts who presented RN, ED volume increased of 169% during treatment. In pts who registered increased ED without RN, the mean ED volume increase during the treatment was of 96,98 %. Pts who presented RN had a mean CTV volume of 56.47 cc. Conclusion PT re-irradiation of rHGG is frequently associated with a significant increase of ED volume during treatment. Such variation often does not translate into clinical worsening and does not need modification of steroid use.ED volume decreases after the end of the treatment.ED volume during treatment increase more in pts who experience RN after re-irradiation and could predict the development of RN.CTV volume does not seem to predict the development of RN. PO-0886 Leptomeningeal metastases of breast and lung cancer- a retrospective analysis I. Hadi 1 , D. Hofmann 1 , R. Bodensohn 1 , M. Niyazi 1 , C. Belka 1 , S. Nachbichler 1 1 University Hospital LMU, Department of Radiation Oncology, Munich, Germany Purpose or Objective Leptomeningeal metastases (LM) might occur in progressive or late stages of solid tumors. Diagnosis and therapy remain challenging due to non-specific symptoms and limited therapeutic options. This retrospective analysis investigated outcome and prognostic factors of patients with LM from breast and lung cancer, who had received radiotherapy at our Institution. Material and Methods Patients with newly diagnosed LM from breast and lung cancer who received radiotherapy at our department were retrieved from the institutional database. Patients treated between 2001 and 2014 were included. The Kaplan-Meier method was performed to analyze survival and log-rank test was used to test differences between groups. Results Forty patients (7 male and 33 female) with a median age of 63 years (range, 31-78 years) were included. LM from breast cancer was found in 25 patients, LM from NSCLC (adenocarcinoma) was found in 15 patients. Median follow- up was 4.5 months (range, 0-75 months) after the start of radiotherapy. All patients underwent whole brain radiotherapy extended to the caudal margin of the second vertebral body with a median single dose of 2.5Gy (range, 1.8-3.0Gy) to a median total dose of 35.0Gy (range, 6.0- 46.0Gy). The majority of patients (n=39, 97.5%) were deceased with a median overall survival of 4.0 months (range, 1.3-6.7months). On univariate analysis, better patients’ performance status (ECOG) improved overall survival (OS) significantly (p=0.031). Symptoms related to intracranial pressure (ICP) or neurological deficits were associated with inferior OS. One year-OS in patients with ICP was 9% and 24.1% in patients without ICP (p=0.034). Histology was not a significant prognostic factor in our cohort (p=0.946). The most common acute toxicities during WBRT were nausea (CTC°3 in 2 patients) and headache (CTC°3 in 2 patients). Improvement or stabilization of neurological deficits after WBRT was observed in 9 patients, one patient did not recover from neurological deficits. Information regarding improvement or stabilization of neurological deficits was not sufficient in 30 patients. Conclusion Our analysis demonstrated that LM from NSCLC and breast cancer were associated with poor overall survival. ECOG and the presence of neurological deficits were significant prognostic factors. WBRT is well tolerated and can provide relief of symptoms. However, further investigations are needed to verify which treatments are the most suitable for different types of LM.