Impact of Radionecrosis and Local Recurrence on Overall Survival After Stereotactic Radiosurgery for Brain Metastases

AbstractPurpose Radionecrosis (RN) is a dose-limiting toxicity after stereotactic radiosurgery (SRS) for brain metastases, and hard to differentiate from treated tumor progression. The outcomes of patients with RN following SRS are not well described, especially in comparison to patients with local CNS progression. Therefore, we characterized 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. 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, 143 patients (10%) had concern for intracranial progression or RN in irradiated sites. Following multi-disciplinary evaluation, 96 patients were ultimately diagnosed with RN and 47 with LR. Patients diagnosed with LR were diagnosed sooner after SRS than RN (median 5.8 vs. 8.3 months, P=0.0087), and patients with LR had worse OS compared to RN (median 15.2 vs. 40.4 months, PP = 0.012), receipt of immunotherapy after SRS (OR = 0.32, P P = 0.028). Conclusion In this multi-institutional cohort study of brain metastasis patients treated with SRS, those with RN had significantly better OS vs. those with LR. These data inform surveillance, diagnosis, and prognosis of these patients