Male Breast Cancer Brain Metastases: Genetic Profiles and Radiosurgery Outcomes.

BACKGROUND AND OBJECTIVES: Male breast cancer (MBC) is very rare, and previous reports of brain metastases (BM) from MBC are limited. To date, the genetic characteristics of MBC with BM have not been explored. In addition, there is only a single case report documenting the use of stereotactic radiosurgery (SRS) for MBC BM. The aim of this study was to summarize genetic alterations associated with BM in patients with MBC and evaluate the safety and efficacy of SRS in this population. METHODS: Four male patients with a total of 20 MBC BMs treated with SRS were retrospectively reviewed. We defined treatment response as complete response, partial response, stable disease, and local progression (LP), per Response Evaluation Criteria in Solid Tumors (RECIST) criteria. The Kaplan-Meier method was used to estimate cumulative incidence rate of LP. RESULTS: The median overall survival was 16.3 months (95% confidence interval: 1.4-31.3 months). The mean age at treatment was 59 years (IQR: 56-60.5 years). Three patients had estrogen receptor-positive lesions, whereas one patient had triple-negative disease. Three patients had notable pathogenic alterations (including in AURKA, BRCA1, BRCA2, CCND1, CHEK2, ERBB2, FLT3, RAF1, and SPINK1). The median lesion size was 5.7 mm (IQR: 3.9-8.6 mm). The median delivered dose was 23 Gy (IQR: 22-24 Gy). Follow-up imaging at 3 months showed a reduction in median lesion size (3.3 mm). The percentage of lesions which were classified as complete response:partial response:stable disease:LP was 0%:45%:55%:0%, respectively. Cumulative 6-month and 12-month local control rates were 100% and 100%, respectively. Only one lesion demonstrated LP at the last follow-up (15 months). CONCLUSION: This is the first report of genetic profiling of MBC with BM and excellent SRS outcomes. The receptor status and genetic alterations across our patients with MBC BM suggest heterogeneity in disease. Larger studies are needed to further explore MBC BM characteristics and treatment outcomes.