RADT-04 IMPROVED SURVIVAL IN PATIENTS WITH RADIONECROSIS VS. LOCAL RECURRENCE AFTER STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES

Abstract PURPOSE: Radionecrosis (RN) is a dose-limiting toxicity after stereotactic radiosurgery (SRS) for brain metastases. How RN affects patient outcomes following SRS is not well described. Therefore, we characterized survival outcomes of patients who develop RN versus treated tumor recurrence in the absence of out-of-field intracranial progression after SRS. METHODS: This cohort study included patients completing an initial course of SRS from 2015-2020 at two institutions. Primary outcome was overall survival (OS) by presence of RN or treated tumor recurrence (LR), analyzed via the Kaplan-Meier method. Binomial logistic regression tested parameters associated with RN or LR. RESULTS: 1383 patients were included, 55% were male and median age was 63.4 years. Common primaries were lung (55%), breast (15%), and melanoma (9%). At a median follow up of 8.7 months, concern for intracranial progression was limited to irradiated sites for 143 patients (10%) - 96 with RN and 47 with LR. LR was diagnosed sooner after SRS than RN (median 5.8 vs. 8.3 months, P=0.0087), and patients with LR had significantly worse OS compared to RN (median 15.2 vs. 40.4 months, P