Gamma knife radiosurgery for breast cancer brain metastasis: survival outcomes, prognotic factors, and the role of repeat treatment.

Purpose: This study evaluated prognostic factors and longitudinal outcomes associated with gamma knife radiosurgery (GKRS) in treating brain metastases from breast cancer, and assessed the efficacy of repeated GKRS in prolonging intracranial disease control.

Methods: In this retrospective study, we reviewed 159 breast cancer patients involving 640 brain metastases who underwent GKRS at a tertiary medical center. Overall survival (OS), local control (LC), and distant intracranial control were estimated using the Kaplan-Meier method. Prognostic factors were estimated using Cox regression models. The effect of repeat GKRS on intracranial disease control was also examined.

Results: The median OS was 19.2 months. In multivariate analysis, the Karnofsky Performance Scale (KPS), HER2 positivity, and ER/PR positivity were independently associated with longer survival. LC rates were 88.9% at 6 months and 83.0% at 12 months. Factors significantly associated with improved LC included a higher margin dose, HER2-negative status, smaller tumor volume, and absence of prior whole-brain radiotherapy (WBRT). Distant intracranial failure within 12 month occurred in 57.0% of patients. Median intracranial control among the 44 patients who underwent repeated GKRS (28.1 months) was significantly longer than those who received single GKRS (8.0 months; p < 0.001).

Conclusion: GKRS provides effective local tumor control and favorable survival outcomes for patients with breast cancer brain metastases. KPS score and receptor status (ER/PR and HER2) are significant predictors of overall survival. Repeat GKRS is a promising strategy for prolonging intracranial control and may reduce the need for WBRT or surgical intervention in selected patients.