ESTRO 2025 - Abstract Book

S704

Clinical - CNS

ESTRO 2025

2599

Digital Poster Stereotactic Radiotherapy in Brain Metastases: SRS/FSRT Paradox and Preferences of Radiation Oncologists in Turkey (TROD 10-010 Study) Berna Akkus Yildirim 1 , Caglayan Selenge Beduk Esen 1 , Sezin Yuce Sari 2 , Enis Ozyar 3 , Yildiz Guney 4 1 Department of Radiation Oncology, Prof. Dr. Cemil Tascioglu City Hospital, Istanbul, Turkey. 2 Department of Radiation Oncology, Hacettepe University Faculty of Medicine, Ankara, Turkey. 3 Department of Radiation Oncology, Acibadem MAA University Faculty of Medicine, Istanbul, Turkey. 4 Department of Radiation Oncology, Etlik City Hospital, Ankara, Turkey Purpose/Objective: Stereotactic radiosurgery (SRS) is one of the main treatment options of brain metastases (BMs) [1]. There is no clear evidence whether single or multiple fractionated stereotactic radiotherapy (FSRT) is superior in terms of local control or toxicity [2]. We aimed to investigate the approach of radiation oncologists’ (ROs) to the treatment of BMs in Turkey. Material/Methods: A 21-question online survey was requested to be filled out by ROs who perform SRS to BMs in Turkey. The test results were presented according to clinical experience (>10 years (senior) and £10 years (junior)) of ROs. Results: One hundred and eleven ROs completed the questionnaire. Eighty-five (77%) among them work as a ROs more than 10 years. ROs most commonly perform linac-based SRS (84%). Although 42% of ROs prefer to perform SRS preoperatively, only 12% of them perform SRS preoperatively in practice. The most common factor affecting the decision of performing SRS instead of whole brain radiotherapy (WBRT) was number of BMs (42%) followed by volume (33%). While the number of BMs was the most considerable factor affecting SRS decision in junior ROs, the other factors have comparable effects with number of BMs among senior ROs (Table 1). The maximum and the minimum number of lesions that physicians were willing to treat with SRS and WBRT was 5 (28%) and 6 (21%), respectively. ROs mostly perform both SRS and FSRT (57%) compared to FSRT (40%) and SRS (4%) (p<0001). Factors that most influence the fraction number decision was volume of BMs (83%), the proximity of BMs to organ at risks (OARs) (76%), size (75%), and the location of BMs (74%), respectively. There was a tendency to treat with SRS compared to FSRT in BMs <2 cm, 4-14 cm 3 , far away from OARs, and which was not treated with WBRT before. Common parameters that are considered for treatment planning were conformity index (86%), V12 Gy of brain (80%), and heterogeneity index (55%), respectively. In follow-up, the most prefferred imaging was spectroscopic and perfusion MRI (94%) for the differential diagnosis of recurrence/radionecrosis in follow-up.