Stereotactic Radiosurgery to greater than 10 brain metastases: Evidence to support the role of radiosurgery for ideal hippocampal sparing in the treatment of multiple brain metastases.

Abstract

BACKGROUND\nBrain metastases are a common occurrence with literature supporting the treatment of a limited number of brain metastases with stereotactic radiosurgery (SRS), as opposed to whole brain radiotherapy. Less well understood is the role of SRS in patients with 10 or greater brain metastases.\n\n\nMETHODS\nPatients treated with SRS to 10 or more brain metastases without concurrent WBRT between March 1999 and December 2016 were reviewed. Analysis was performed for overall survival (OS), treated lesion freedom from progression (FFP), freedom from new metastases (FFNM), and adverse radiation effect (ARE). Hippocampal volumes were retrospectively generated in patients treated with upfront SRS for evaluation of dose volume metrics.\n\n\nRESULTS\nA total of 143 patients were identified with 75 having upfront SRS and 68 being treated as salvage therapy after prior WBRT. The median number of lesions per patient was 13 (IQR 11-17). Median total volume of treatment was 4.1 cc (IQR 2.0-9.9). The median 12-month FFP for upfront and salvage treatment was 96.8% (95% CI: 95.5-98.1) and 83.6% (95% CI: 79.9-87.5), respectively (p < 0.001). Twelve month FFNM for upfront and salvage SRS was 18.8% (95% CI: 10.9-32.3) versus 19.2% (95% CI: 9.7-37.8), respectively (p = 0.90). The mean hippocampal dose was 150 cGy (IQR 100-202).\n\n\nCONCLUSIONS\nExcellent rates of local control can be achieved when treating patients with greater than 10 intracranial metastases either in the upfront or salvage setting. Hippocampal sparing is readily achievable with expected high rates of new metastatic lesions in treated patients.