ESTRO 2025 - Abstract Book

S663

Clinical - CNS

ESTRO 2025

Conclusion: We demonstrated that among TN patients, higher dose-rates may be associated with improved pain relief following GKRS. As there are few studies assessing GKRS dose-rate on clinical outcomes, further primary studies should be conducted to allow for meta-analysis and higher certainty of evidence.

Keywords: gamma knife radiosurgery, Cobalt 60, dose-rate

References: 1. Desai R, Rich KM. Therapeutic Role of Gamma Knife Stereotactic Radiosurgery in Neuro-Oncology. Mo Med. 2020;117(1):33-8. 2. Monaco EA, Grandhi R, Niranjan A, Lunsford LD. The past, present and future of Gamma Knife radiosurgery for brain tumors: the Pittsburgh experience. Expert Rev Neurother. 2012;12(4):437-45. 3. Kann BH, Yu JB, Bond J, Loiselle C, Chiang VL, Bindra RS, et al. The impact of cobalt-60 source age on biologically effective dose in stereotactic radiosurgery thalamotomy. International Journal of Radiation Oncology. 2016;96(2 Supplement 1):E563.

581

Digital Poster Evaluation of a fractionated stereotactic postoperative radiotherapy regimen for brain metastasis Sebastian H. Maier 1,2 , Alexander Nitschmann 1 , Coralia Dehelean 1 , Vasiliki Anagnostatou 1,2 , Sylvia Garny 1 , Montserrat Pazos 1 , Sebastian N. Marschner 1,3 , Stefanie Corradini 1 , Claus Belka 1,2,3 , Niklas Thon 4,3 , Maximilian Niyazi 1,5,6 , Raphael Bodensohn 1,5,6 , Stephan Schönecker 1,2 1 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany. 2 Bavarian Cancer Research Center, BZKF, Munich, Germany. 3 German Cancer Consortium (DKTK), Partner Site Munich, A Partnership between DKFZ and LMU University Hospital, Munich, Germany. 4 Department of Neurosurgery, University Hospital, LMU Munich, Munich, Germany. 5 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 6 Center for Neuro-Oncology, Comprehensive Cancer Center Tübingen-Stuttgart, University Hospital Tübingen, Tübingen, Germany Purpose/Objective: Brain metastasis (BM) occur in up to 40% of patients with solid tumors. Following surgical removal, postoperative radiotherapy is typically administered to the resection cavity to prevent recurrence. However, ideal prescription and fractionation remain uncertain. As part of a single-center study, we aimed to evaluate a specific concept. Material/Methods: We conducted a retrospective analysis of patients who received postoperative daily stereotactic fractionated radiotherapy (SFRT) (5x5Gy, 80% isodose) for completely resected BM between 2017 and 2024 at our center. The target volume was the resection cavity with the inclusion of a 2mm PTV margin. Only resection cavities without residual tumor were included in the analysis. The study aimed to evaluate local control and occurrence of radionecrosis as primary endpoints. Secondary outcomes included overall survival (OS) and intracranial progression-free survival (iPFS). Kaplan-Meier analyses were calculated from the first day of fractionated irradiation. In cases where whole brain irradiation (WBRT), due to new intracranial metastases, was performed, local control was censored at the time of the procedure. Results: A total of 149 patients (60 male, 89 female) with 163 resection cavities were included in the study. The median age was 62 years (range 32-86 years). Median follow-up time was 36 months. A total of 36% of patients had a Karnofsky Performance Status Scale (KPS) of at least 90% prior to radiotherapy, while only 9% had a KPS of less than 70%. The most prevalent diagnosis was metastatic non-small cell lung cancer (38%), followed by breast cancer (17%),