ESTRO 2020 Abstract Book

S477 ESTRO 2020

Purpose or Objective Immune checkpoint blockers (ICB) targeting the PD-1/PD- L1 axis are an integral component in cancer therapy. They are used both as monotherapy and in various treatment combination concepts. In case of brain metastases, radiation therapy (RT) is frequently added in treatment management. We analyzed acute and late adverse events of patients with cerebral metastases of different tumor types treated with RT and parallel or non-parallel application of ICB. Material and Methods Retrospectively we analyzed treatment related toxicities according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 of all patients being treated at our center from 2013 to 2017 with RT to brain metastases and anti-PD-1 therapy simultaneously or with at least 1-month interval between both therapies. All tumor types and RT concepts were included. Adverse events were compared using cross-tables and the Chi-square test with SPSS v. 26. Results 55 patients with 80 brain metastases were analyzed. 31 of those patients were treated in parallel, 24 received both therapies consecutively. Either pembrolizumab (n=36) or nivolumab (n=19) was applied. The most frequently observed side effects in the whole patient cohort were fatigue (31%), pruritus (23%), and nausea (22%). We detected more acute (91 events) than late (6 events) side effects with CTCAE grades from 1-3. Grade 3 events were rare and included only acute side effects and were evenly distributed in both groups (4 and 5 events). In the group of patients treated in parallel, we found 65 acute side effects, compared to 26 in the group not treated simultaneously. Statistically significant differences were observed regarding headache (p=0.031) and nausea (p=0.008) with more events in the group treated in parallel. Conclusion Patients who are irradiated for brain metastases and receive PD-1 inhibitors simultaneously have more acute side effects than patients undergoing both treatments but not at the same time. We observed especially more nausea and headache in this patient group. This might be due to the invasion of immune cells to the RT field leading to local reactions like pseudoprogression. To prove this, further analyses are ongoing. Overall, the severity of toxicities was moderate with few grade 3 events. Late side effects were rare and evenly distributed in both treatment groups. We consider the application of both treatments at the same time to be safe and applicable in clinical routine. Additional investigations are needed to determine if the application of RT to brain metastases and ICB simultaneously leads to an improvement of oncological endpoints. PO-0892 Hypofractionated stereotactic radiotherapy for meninigioma, multicentric serie M.P. Sunyach 1 , M. Pernod 1 , C. Carrie 1 , B. Pierre Yves 2 1 Centre Leon Berard, Rhone, Lyon cedex 08, France ; 2 Centre Antoine Lacassagne, Alpes Maritimes, Nice, France Purpose or Objective Introduction: Meningiomas represent 30% of intracranial tumors. Only progressive tumours and/or symptomatic or high-grade have an indication for treatment. For progressive or symptomatic tumours, surgery is the reference treatment. When this is not possible, exclusive radiotherapy (RT) is proposed. Depending on the topography of the meningiomas and their size, there are several radiotherapy techniques. The hypofractionated stereotactic radiotherapy (hSRT) allows to treat larger volumes than SRS while keeping the radiobiological benefit of hypofractionation. This technique is currently available in more and more centres. Local control and tolerance of hSRT are poorly evaluated in the literature. The objective

of this series is to analyze the practices of two centres, and also to focus on clinical benefits by analysing the

evolution of symptoms. Material and Methods

Materials and methods: Our study was retrospective and multicentric (CLB and Nice). We have included patients between 2007 and 2013 for intracranial meningiomas treated with hSRT by Cyberknife. We excluded patients with concomittant cerebral pathologies, particularly in the context of neurofibromatosis. We studied the neurological symptoms before treatment with Cyberknife and their progression throughout the follow-up (taking into account possible aggravations after radiotherapy) as well as tumor Results: 96 lesions were treated, the median follow-up was 4.4 years. The assessment was done for each symptom. We also performed an overall neurological score for each patient and evaluated the evolution of this score at the over time. At the last news this score was significantly improved p<0.0001 (1.8-1). In The 54 patients (56.3%) 95% CI (45.8% - 66.4%) the global neurologic score is improved after radiotehrapy. Patients with exclusive RT have greater benefice compared to patients treated at recurrence or with post operative irradiationp=0.0015. Survival without recurrence was 76% at 5 years. Overall survival was 95.2% at 5 years. Event free survival was 57% control. Results Conclusion: hSRT radiotherapy is a well-tolerated technique. It improves symptoms neurological and those in particular when it is exclusive. PO-0893 Radiation therapy in meningioma- single center prospective and retrospective analysis I. Hadi 1 , P. Yanchovski 1 , R. Bodensohn 1 , S. Corradini 1 , C. Schichor 2 , C. Belka 1 , M. Niyazi 1 1 University Hospital LMU, Department of Radiation Oncology, Munich, Germany ; 2 University Hospital LMU, Department of Neurosurgery, Munich, Germany Purpose or Objective Meningioma is the most common primary intracranial tumor in adults. However, management of meningioma has not changed significantly until recently. Therefore, we analyzed patients, who underwent radiation therapy at our institution both prospectively and retrospectively. Material and Methods Every patient with meningioma who received radiation therapy at our department was included. All patients were diagnosed with MRI of the brain and 68 Ga-DOTATATE PET/CT prior to radiotherapy. Visual test, audiometry and hormonal testing were performed based on the localization of meningioma. These tests were carried out at baseline and follow up. The Kaplan-Meier method was used to analyze local control and log-rank test was used to test for differences between groups. Results This is an interim analysis of 78 out of 227 patients with meningioma, who have been treated at our institution between 2011 and 2019. Fifty-six female (71.8%) and 22 male (28.2%) patients with a median follow-up of 11 months (range: 3-42 months) were included in this first analysis. Meningioma WHO°I was found in 63 patients (80.8%), WHO°II in 14 patients (17.9%), and WHO°III in 1 patient (1.3%). WHO °I patients were treated with a median single dose of 1.8Gy to a median total dose of 54.0Gy. WHO°II and °III patients received radiotherapy in a median single dose of 1.8Gy to a median total dose of 59.4Gy. One- and 2-year local control in patients with WHO°I meningioma after radiotherapy were both 100% respectively. Twelve-months LC in patients with WHO°II meningioma was 87.5%. Radiotherapy was well tolerated, with no CTCAE °III was reported. The most common at 5 years. Conclusion