Abstract P6-11-03: Follow up of breast cancer patients who underwent gamma knife radiosurgery for a diagnosis of brain metastases: A single institutional experience

Abstract

Abstract Background: Breast cancer (BC) is the second most common cause of brain metastases in the United States. We performed a retrospective analysis of BC patients (pts) in the Yale Gamma Knife Radiosurgery (GKRS) database treated for brain metastases (mets) to report overall survival (OS) from time of GKRS, and to identify factors that predict improved survival outcomes. Methods: We performed retrospective review of the Yale database of BC pts treated with standard GKRS technique for brain mets from 2000 to May 2013. Treatment doses typically ranged from 16 to 24 Gy prescribed to the 40-85% isodose surfaces. Overall survival (OS) for each patient was calculated from the date of first GKRS treatment of brain metastases. Variables included age, Karnofsky Performance Status (KPS), pre/post whole-brain radiation treatment (WBRT) and/or surgical resection, and # of brain mets treated (1-4 vs ≥5). Results: A total of 80 BC pts were identified, with a mean age of 56.2 yrs; KPS 40-60 in 8pts (10%), 70-80 in 13 (16%), 90-100 in 41 (51%), unknown in 18 (23%); ER+ in 38 (48%), ER- in 38 (48%), unknown in 4 (5%); HER2 + in 38 (48%), HER2- in 33 (41%), indeterminate in 3 (4%) and unknown in 6 (8%). BC subtypes are Luminal A (ER+/HER2-) in 16 (20%), Luminal B (ER+/HER2+) in 19 (24%), HER-2(ER-/HER2+) in 17 (21%), Basal (ER-/HER2-) in 17 (21%), unknown in 11 (14%). Number of brain mets at time of first GKRS ≥5 in 32 (40%); prior WBRT in 30 (38%); WBRT post GKRS in 9 (11%); surgical resection for brain mets in 13 (16%) prior to GKRS and post GKRS in 9 (11%); 16% had ≥3 GKRS. Median time from primary BC dx to brain mets is 62.8 months (m) (range 46.2-81.6); with no significant difference among subtypes. Median OS from GKRS is 13.1 m (7.6-21.9); median OS from brain mets is 18.8 m (11.7-23.9). On univariate analysis, factors associated with significant improved OS from time of GKRS included HER-2 subtype (p = 0.005), KPS 90-100 (p = 0.008), good control of systemic disease (p = 0.017), pre (p = 0.041) and post GKRS surgical resection (p = 0.02). Age, pre or post WBRT, # of brain mets (1-4 vs. 5) were not significant predictors of OS from time of GKRS. In a multivariate Cox analysis (46 cases), HER-2 subtype remained a significant predictor of improved OS from time of GKRS; (HR) 0.26, 95%CI 0.08 to 0.8, p-value = 0.02. There was a trend in favor of surgical resection of brain mets pre GKRS (HR 0.14, 95% CI 0.02 to 1.15, p-value = 0.067 Conclusion: GKRS offers good local control for BC pts with brain mets, and is a reasonable option for pts with ≥5 brain mets. Our results show no associated survival benefit for administration of WBRT pre/post GKRS. HER-2 subtype is a significant predictor of improved survival in BC pts undergoing GKRS for brain mets. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-11-03.