P11.33.B CHARACTERISTICS OF LONG-TERM SURVIVORS AMONG PATIENTS WITH BRAIN METASTASES TREATED WITH RADIOTHERAPY

Abstract BACKGROUND The incidence of brain metastases in the adult cancer population is rising. Thanks to advances in systemic therapies and evolving radiotherapy strategies, survival rates continue to improve. However, little is known about who these long-term surviving patients are and what their clinical course or outcomes are following treatment. In this study we describe the clinical characteristics of long-term survivors (LTS). MATERIAL AND METHODS Data were obtained from the Cohort for patient-reported Outcomes, Imaging and trail inclusion in Metastatic BRAin disease (COIMBRA) from May 2019 until December 2023. Clinical information on survival, disease progression, and cancer treatments during the year following radiotherapy was collected from hospital medical records. Patients were classified as long-term survivors (LTS; >1 year survival) or short-term survivors (STS; ≤1 year survival) after radiotherapy for brain metastases. PRELIMINARY RESULTS Within this time period, 481 patients were included in the COIMBRA study. Of these, 258 individuals (54%) were LTS. The median survival time among LTS was 553 days (approximately 18 months and 5 days), compared to 155 days (5 months and 3 days) in STS. The majority of patients received SRS (88% of STS and 98% of LTS). Lung cancer, breast cancer, and melanoma were the most common primary tumors among both the LTS and STS. The distribution of pre-radiotherapy characteristics among LTS—such as primary tumor type, number of brain metastases, and KPS—was largely comparable to that of the overall cohort, with the exception of melanoma, which was more prevalent among LTS. This suggests no clear survival advantage for most subgroups, apart from a possible association with melanoma. Notably, 60% of LTS developed new brain metastases during the first year following radiotherapy, of whom 68% underwent re-irradiation. CONCLUSION Over half of the patients treated with radiotherapy for brain metastases survived longer than one year - challenging the historically poor survival reported in this population. Long-term survivors showed no distinct pre-radiotherapy characteristics compared to the overall cohort, except for a higher prevalence of melanoma, suggesting that extended survival is generally not limited to specific clinical subgroups. These findings underscore the importance of recognizing the substantial proportion of long-term survivors and the growing need to critically assess the long-term impact of treatments and optimize follow-up care.