ESTRO 2022 - Abstract Book

S984

Abstract book

ESTRO 2022

Results In total, 31 patients were assessed including six (19.4%) patients in group 1, seven (22.6%) in group 2 and 18 (58.1%) patients in group 3. Median follow-up was not reached in group 1, 55.7 months in group 2 and 33.1 months in group 3. Median overall survival after diagnosis of MBM was 13.9 months (95% CI 11.4-16.3) in group 1, not reached in group 2 and 16.3 months (95% CI 12.1-23.7) in group 3. Intracranial progression-free survival was 2.5 months (95% CI 2.4-2.5) for group 1, 10.9 months (95% CI 2.3-19.5) for group 2 and 1.5 months (95% CI 1.2-7.2) for group 3. In total, there were ten (32.3%) patients with reported CTCAE grade 3 toxicities. Five (16.1%) of them were related to SRS (radionecrosis or hemorrhage CTCAE grade 3). All of these five patients were in group 3, which was significantly related to CTCAE grade 3 toxicities (p=0.050). Moreover, all of these patients received SRS within seven days of IPI+NIVO treatment; to receive SRS within seven days of IPI+NIVO treatment was therefore significantly related to grade 3 toxicities (p=0.036), Conclusion The patient group in which SRS was applied during or less than seven days before or after IPI+NIVO showed significantly higher grade 3 toxicities than the patient groups with sequential treatment. Due to the small cohort and the retrospective nature of this study, there is however a relevant selection bias with concomitant treatment mainly chosen for patients with dismal prognosis of MBM. Thus, the results should be confirmed in a larger prospective cohort. 1 University Hospital, Department of Radiation Oncology, Bonn, Germany; 2 University hospital, Department of Radiology, Bonn, Germany; 3 University Hospital, Division of Clinical Neuro-Oncology, Department of Neurology, Bonn, Germany; 4 University Hospital, Department of Neurosurgery, Bonn, Germany Purpose or Objective Primary gliosarcoma (GS) is a rare variant of IDH -wildtype glioblastoma multiforme. We performed a single center analysis to identify prognostic factors. Materials and Methods We analysed the records of 26 patients newly diagnosed with primary WHO Grade IV GS. Factors of interest were clinical and treatment data, as well as molecular markers, time to recurrence, and time to death. Results The median follow-up was 9 months (range from 5 to 21 months). Low symptom burden at the time of diagnosis was associated with longer PFS (P = 0.023) and OS (P = 0.018). The median OS in the entire cohort was 12 months. Neither MGMT promoter hypermethylation nor adjuvant temozolomide therapy influenced survival, in consistency with some previous reports. Conclusion In this retrospective study, patients exhibiting low symptom burden at diagnosis showed improved survival. None of the other factors analysed were associated with altered outcome. D.H. Kannikanti 1 , F. Charlwood 1 , M. Clarke 1 , R. Colaco 1 , S. Pan 1 , D. Saunders 1 , P. Sitch 1 , N. Thorp 1 , G. Whitfield 1,2 , M. Rasool 3 1 The Christie NHS Foundation Trust, Proton Beam Therapy Centre, Manchester, United Kingdom; 2 Division of Cancer Sciences, University of Manchester, Manchester Cancer Research Centre, Manchester Academic Health Science Centre, Manchester, United Kingdom; 3 University of Manchester, School of Medicine, Manchester, United Kingdom Purpose or Objective Adjuvant radiotherapy in ependymoma improves both local control and survival outcomes. The 5 year overall survival in paediatric ependymoma is around 85%. With such outcomes, the late effects of treatment assume prime importance. Protons when compared with photons have the potential to spare organs at risk (OARs), and thereby decrease late complications. This study was designed to compare the dosimetry of proton with photon radiotherapy plans in patients with posterior fossa ependymoma, in order to understand the potential for reduced late effects. Materials and Methods Data were extracted for ten patients with posterior fossa ependymoma treated with protons who had Volumetric Modulated Arc Therapy (VMAT) photon plans prepared in case of cyclotron downtime. Five were single phase plans to a total dose of 59.4Gy in 33 fractions, with appropriate limitation of dose at spinal cord level, and 5 were two phase plans, to 54Gy in 30 fractions followed by a boost of 5.4Gy in 3 fractions to the volume above the foramen magnum. Clinically relevant dosimetric variables of target and routinely outlined OARs for data collection were selected based on our clinical practice and with reference to the European Particle Therapy Network (EPTN) consensus on radiation dose constraints for OARs in neuro-oncology. Mean values were compared between proton and photon plans using a two tailed paired sample t-test. P values of less than 0.05 were considered statistically significant. PO-1160 Chasing a rarity: a retrospective single centre evaluation of prognostic factors in gliosarcoma M. Koeksal 1 , C. Dejonckheere 1 , A. Böhner 2 , U. Herrlinger 3 , H. Vatter 4 , F.A. Giordano 1 PO-1161 Protons in posterior fossa ependymoma- a dosimetric comparison with photons