Initial SRS for Patients With 5 to 15 Brain Metastases: Results of a Multi-Institutional Experience

Several studies evaluating stereotactic radiosurgery (SRS) for patients with >4 brain metastases (BM) demonstrated similar outcomes after treatment of 1, 2 to 4, and 5 to 15 BM; others found clinically significant survival decrements in the latter group. In this review of 8 academic centers, we compared outcomes of patients undergoing initial SRS for 1, 2 to 4, and 5 to 15 BM. A total of 2089 patients treated with initial SRS for BM were included. Overall survival (OS) was estimated using the Kaplan-Meier method and compared using the log-rank test. Patient and disease characteristics were evaluated for association with OS and cumulative incidence of distant brain failure (DBF) using stepwise multivariable Cox proportional hazards and competing risk regression modeling. In this series, 989 (47%) patients had 1 metastasis, 882 (42%) had 2 to 4 metastases, and 212 (10%) had 5 to 15 metastases treated. Median OS for the 1, 2 to 4, and 5 to 15 BM groups was 14.6, 9.5, and 7.5 months, respectively (log-rank P