Factors Influencing the Outcome of Stereotactic Radiosurgery in Patients With Five or More Brain Metastases

Background: Stereotactic radiosurgery (SRS) for patients with 5 or more brain metastases (BMets) is a matter of debate. We report our results with that approach and the factors influencing outcome. Methods: In the 103 patients who underwent SRS for the treatment of 5 or more BMets, primary histology was non-small-cell lung cancer (57% of patients). All patients were grouped by Karnofsky performance status and recursive partitioning analysis (RPA) classification. In our cohort, 72% of patients had uncontrolled extracranial disease, and 28% had stable or responding systemic disease. Previous irradiation for 1–4 BMets had been given to 56 patients (54%). The mean number of treated BMets was 7 (range: 5–19), and the median cumulative BMets volume was 2 cm³ (range: 0.06–28 cm³). Results: Multivariate analyses showed that stable extracranial disease (p < 0.001) and RPA (p = 0.022) were independent prognostic factors for overall survival (OS). Moreover, a cumulative treated BMets volume of less than 6 cm³ (adjusted hazard ratio: 2.54; p = 0.006; 95% confidence interval: 1.30 to 4.99) was associated with better OS. The total number of BMets had no effect on survival (p = 0.206). No variable was found to be predictive of local control. The RPA was significant (p = 0.027) in terms of distant recurrence. Conclusions: Our study suggests that SRS is a reasonable option for the management of patients with 5 or more BMets, especially with a cumulative treatment volume of less than 6 cm³.