ESTRO 2022 - Abstract Book

S983

Abstract book

ESTRO 2022

Eleven of the patients were WHO grade 3 anaplastic astrocytomas, and 48 of the patients were WHO grade 4 glioblastomas. All of the patients received a median of 60 Gy (59.4-60 Gy) of postoperative radiotherapy (RT), and 51 of them received oral temozolomide chemotherapy, concurrently. The median time to first recurrence was 13 (4-85) months. 12 of the patients had a second surgery before re-irradiation. SRT was performed as a median prescription dose of 30 Gy (range 15- 30), with a median of 5 fractions (1–5). The median follow-up time was 4 months (range 1–57), 11 patients were alive at the last follow-up. The median OS after re-irradiation was 8 (95% CI: 4.66-11.33) months, and 1- and 2-y OS were 33.2% and 14.2%, respectively. In the univariate analysis, age <65 years (p =0.003), grade 3 gliomas (p =0.023), size of tumor <2cm (p=0.018) were associated with better survival. Grade 3 gliomas (p =0.027), size of tumor <2cm (p=0.008) were remained independent prognostic factors for OS in the multivariate analysis. Recurrence after re-irradiation was detected in 20 patients, 6 of them belonged to new lesions. The median PFS after re-irradiation was 5 (95% CI: 3.39-6.60) months, and 1- and 2-y PFS were 24.5% and 9.5%, respectively. In the univariate analysis, age <65 years (p =0.033), grade 3 gliomas (p =0.037), stable response at first evaluation with magnetic resonance imaging (p=0.003), and time to recurrence >9 months (p=0.021) were associated with improved PFS. Stable response (p =0.001) was remained prognostic factor for PFS in the multivariate analysis. LCR were 62.7% and 33.9% at the first and last follow up. There was no serious toxicity. Conclusion SRT is a viable treatment modality with significant survival contribution in recurrent HGG. It should be considered when deciding on re-irradiation during follow-up, as it may have a favorable prognostic effect on survival in patients with tumor size <2 cm.

PO-1159 Stereotactic radiosurgery and combined immunotherapy with ipilimumab and nivolumab for melanoma brain metastases R. Bodensohn 1 , S. Werner 1 , J. Reis 2 , M. Pazos Escudero 1 , A. Kaempfel 1 , I. Hadi 1 , R. Forbrig 2 , F. Manapov 1 , S. Corradini 1 , C. Belka 1 , S. Theurich 3 , L. Heinzerling 4 , M. Schlaak 5 , M. Niyazi 1 1 University Hospital LMU Munich, Department of Radiation Oncology, Munich, Germany; 2 University Hospital LMU Munich, Institute of Neuroradiology, Munich, Germany; 3 University Hospital LMU Munich, Department of Medicine III, Munich, Germany; 4 University Hospital LMU Munich, Department of Dermatology and Allergology, Munich, Germany; 5 Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Dermatology, Venereology and Allergology, Berlin, Germany Purpose or Objective Adding stereotactic radiosurgery (SRS) to combined immune checkpoint therapy with ipilimumab and nivolumab (IPI+NIVO) has led to promising results for patients with melanoma brain metastases (MBM). Previous studies have shown a synergistic effect. However, the toxicity especially with regard to radionecrosis has been unclear. This study retrospectively analyzes the toxicity profile depending on the timing of SRS during IPI+NIVO. Materials and Methods For this study, the clinical database was searched for all patients with MBM who were treated with SRS and IPI+NIVO. The patients were separated into three groups: group 1 received IPI+NIVO (usually up to four cycles) more than 14 days before SRS, group 2 IPI+NIVO more than 14 days after SRS, and group 3 received SRS concurrently to IPI+NIVO. All groups were compared with respect to overall survival, progression-free survival and toxicity. Toxicity was graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 5. The follow-up MRIs were evaluated by two experienced neuroradiologists. Relation between groups and toxicity was analyzed using the Fisher-Yates-test.