RADI-32. INTRACRANIAL CONTROL AND RADIONECROSIS IN MELANOMA PATIENTS WITH BRAIN METASTASES TREATED WITH STEREOTACTIC RADIOSURGERY

PURPOSE/OBJECTIVE(S): Melanoma commonly metastasizes to the brain and is radioresistant. Stereotactic radiosurgery (SRS) confers durable local control of brain metastases (BM) while maintaining neurocognitive function. These advantages are increasingly important as survival among these patients improves secondary to advances in systemic therapies. This study investigated the local control (LC), intracranial PFS (iPFS), freedom from radionecrosis (FFRN), and overall survival (OS) among melanoma patients receiving SRS for BM. MATERIALS/METHODS: We retrospectively reviewed clinical outcomes of melanoma patients with brain metastases treated with SRS between October 2008 and January 2017 in a large academic centre. Post-SRS, patients were followed in a multidisciplinary clinic with clinical examination and brain MRI every 3 months. Survival outcomes were estimated using the Kaplan-Meier method. RESULTS: In total, 97 patients with 283 brain metastases (including 12 surgical cavities) treated with SRS were identified. Median age was 60.5 (24.4–90.7). Median follow-up was 9.6 (2.2–74.7) months after first SRS. Median prescription dose was 21 (10–24) Gy delivered in a single fraction. Thirty (30.9%) patients had WBRT post-SRS, 36 (37.1%) patients had BRAF-positive disease. Per lesion (N=283), 1-year LC and FFRN were 84.4%, and 90.1%, respectively; medians were not achieved for either LC or FFRN. Radionecrosis (RN) occurred in 20 (7.1%) lesions. Per patient (N=97), median OS and iPFS were 16.0 and 5.3 months, respectively; 1-year OS and iPFS rates were 62.0%, and 30.1%, respectively. CONCLUSION: SRS resulted in excellent rates of LC, with a low risk of RN. However, most patients developed intracranial progression within 1 year. Further analyses to establish correlates (lesion size, SRS dose, and molecular status) to LC, FFRN, OS, and iPFS will be performed prior to the final presentation.