Stereotactic Radiosurgery to the Resection Cavity in Patients with Brain Metastases: Patterns of Failure and Prognostic Factors

OBJECTIVE The objective of this study was to extensively analyze failure patterns of patients who received single or multi-fraction stereotactic radiosurgery (SRS) to the surgical cavity and to identify prognostic factors for recurrence and survival metrics. METHODS Patients with brain metastases who underwent surgical resection and then had SRS to the surgical cavity, between 2010 and 2021, at our department were identified. Local failure (LF), distant failure (DF), leptomeningeal disease (LMD), overall survival (OS), and salvage whole brain radiotherapy (WBRT) rates were calculated. Patient or treatment-related variables were evaluated for association with LF, DF, LMD, and OS. RESULTS Fifty- three patients with total of 54 operated metastases were identified. The median follow-up period was 13 months. Cumulative incidence rates of LF, LMD, and DF were 15%, 11%, and 37% at 1 year, respectively. Salvage WBRT was employed in 13 (26%) patients. DF was less frequent in patients with breast cancer primary compared to patients with other primaries (p= 0.048, Hazard ratio [HR]:0.28) on univariate analysis. One-year OS rate was 54%. Median survival was 17 months. Eastern cooperative oncology group (ECOG) 0 performance status (p=0.0113; HR:0.328), being without active extra-cranial metastasis at the time of brain SRS (p=0.0035; HR:0.321), and metachronous brain metastases (p=0.0191; HR:0.399) were determined as statistically significant prognostic factors of survival on multivariate analysis. CONCLUSION SRS to surgical cavity seems optimal treatment modality especially for the patients with one of the following factors including ECOG 0 performance status, not having an active extracranial metastasis at the time of SRS, and metachronous brain metastases.