Stereotactic radiosurgery for brain metastases from male breast cancer: a multicenter retrospective study

Purpose: Brain metastases (BMs) from male breast cancer (MBC) are exceptionally rare, and the efficacy and safety of stereotactic radiosurgery (SRS) in this population remain poorly characterized. Methods: We conducted a multicenter retrospective cohort study across 12 institutions. Eligible patients had histologically confirmed MBC with histopathologically or radiologically documented BMs treated with SRS. Lesion-level outcomes were analyzed using generalized estimating equations (GEE) with robust variance estimation. Overall survival (OS) was estimated by the Kaplan-Meier method. Neurological symptom change was assessed with McNemar’s exact test, and discriminative ability of dosimetric variables for local failure was evaluated using receiver operating characteristic (ROC) analysis. Results: Nineteen patients harboring 185 SRS-treated lesions were included. Median age at SRS was 59.0 years. The overall crude local control rate was 97.3%. Median OS was 28.0 months. Patients with controlled systemic disease at SRS demonstrated significantly longer median OS than those without (40.0 vs. 22.0 months; p = 0.032). Target volume was the only significant discriminator of local failure on ROC analysis (p < 0.001; optimal threshold 0.98 cc) and independently predicted adverse radiation effects on GEE analysis (p = 0.013). Neurological symptom burden decreased significantly after SRS (63.2% to 26.3%; p = 0.016), and median Karnofsky Performance Status remained stable. Conclusion: SRS achieves high local control with a favorable safety and neurological profile in MBC BMs. Systemic disease control at the time of SRS is the primary determinant of survival, while target volume is the principal dosimetric predictor of both local failure and radiation toxicity. These findings support the application of established SRS practice parameters in this rare population.