P11.14.A STEREOTACTIC RADIOSURGERY FOR OVARIAN CANCER BRAIN METASTASES: AN INTERNATIONAL RADIOSURGERY RESEARCH FOUNDATION RETROSPECTIVE STUDY

Abstract BACKGROUND Ovarian cancer rarely metastasises to the brain, thus studies reporting the outcomes of affected patients are lacking. Stereotactic radiosurgery (SRS) is now the mainstay of management for patients with brain metastases (BM) from most primary sites, but little evidence of its efficacy in ovarian cancer is available. The current study was undertaken to provide guidance for SRS management using pooled data from multiple institutions. MATERIAL AND METHODS Centers participating in the IRRF (International Radiosurgery Research Foundation) were asked to provide outcome data for patients who had SRS for ovarian cancer brain metastases between 2020 and 2024 and at least one clinical and imaging follow-up after the procedure. Primary endpoints included survival from SRS, local tumor response according to RANO-BM criteria and occurrence of adverse radiation effects (ARE). Cox regression analyses were performed to identify variables impact each endpoint. RESULTS 128 patients had SRS for a total of 532 BM treated. Epithelial histology was the most common (91%). Median age at SRS was 62 years (IQR 56-70). Median KPS was 80% (IQR 80-90%) and 71.9% of patients had neurological symptoms at presentation. Other active systemic metastases were present in 41.4%. The median number of treated BM was 2 (IQR1-3) and the median cumulative treatment volume was 6 cc (IQR 2-12.9). The median margin dose was 18 Gy (IQR 16-20). At last follow-up, 19.5% of patients were still alive. The median overall survival (OS) after SRS was 27 months, and 6-, 12- and 24-month OS was 83.8%, 74.2% and 52.2%, respectively. Multivariate analyses revealed that increasing age at SRS (HR 1.02, p=0.05), active systemic metastases (HR 2, p=0.005) and increasing number of brain metastases (HR 1.05, p=0.04) were associated with worse survival, while repeating SRS (HR 0.4, p=0.002) led to improved survival. Local failure occurred in 12.8% of treated BM. Actuarial progression-free survival (PFS) at 6, 12 and 24 months was 92.3%, 86.6% and 70.3%, respectively. Only prior WBRT (HR 4.36, p=0.03) led to worse local control on multivariate analyses. New remote BM appeared in 49.5% of patients and 14.5% suffered from leptomeningeal dissemination. ARE were seen in 12.1% of BM but were symptomatic in only 3.2%. On multivariate analyses, prior SRS (HR 3.13, p=0.002) was associated with increased risk of ARE. CONCLUSION Ovarian cancer brain metastases can be safely and effectively managed with SRS as the primary treatment modality in most patients.