Brain metastases from breast cancer: Survival by HER2 status in the trastuzumab era

Abstract

779 Background: Brain metastases from breast cancer develop in 15% to 30% of women with metastatic breast cancer. Survival after brain metastases from breast cancer was assessed in the era of trastuzumab. Methods: Women with brain metastases from breast cancer that were treated or evaluated at the Massachusetts General Hospital since 1998 were retrospectively identified through hospital records or databases in the Department of Radiation Oncology and Neuro-Oncology. 109 women were identified as having breast cancer that metastasized to the brain. Tumors were classified as HER2 overexpressed if HER2 immunohistochemistry (IHC) was reported as 3+ or if Her2 gene amplification was present by fluorescent in situ hybridization (FISH). Tumors were classified as HER2 non-overexpressed if HER2 IHC was 1+ or if the Her2 gene was not amplified by FISH. Age at primary breast cancer diagnosis, time to develop brain metastasis, and survival after developing brain metastasis were compared for patients stratified by HER2 status. Results: In 91 of the 109 patients, HER2 status could be evaluated. 46 patients had tumors that did not overexpress HER2, while 45 patients had tumors that did overexpress HER2. 35 of these patients were treated with trastuzumab. There was no statistically significant difference between the age of primary breast cancer diagnosis (mean 48.1 years) or time to develop brain metastases (mean 58.2 months) according to HER2 status. However, patients with HER2 overexpressing breast cancer had a significantly longer overall survival (median 23 months vs. 10 months) after the development of brain metastases (p=0.0016 by log rank test). Conclusions: In the trastuzumab era, women with brain metastases with HER2 overexpressing breast cancer have a significantly improved survival. Better systemic disease control with HER2-targeted therapy may account for the improved survival for patients with HER2 overexpressing brain metastases. Further gains would likely result from HER2-targeted therapy that can cross the blood-brain barrier. No significant financial relationships to disclose.