Breast cancer subtypes and response to systemic treatment after whole-brain radiotherapy in patients with brain metastases

Abstract

Background: The aim of this study was to assess the role of systemic treatment after whole-brain radiotherapy (WBRT) in immunohistochemically defined biological subsets of breast cancer patients with brain metastases.

Methods: The group of 420 consecutive breast cancer patients with brain metastases treated at the same institution between the years of 2003 to 2009 was analyzed. Patients were divided into 4 immunohistochemically biological subsets, based on the levels of estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2) receptors, and labeled as luminal A, luminal B, HER2, and triple-negative. Survival from brain metastases with and without systemic treatment after WBRT was calculated in 4 subsets.

Results: In the entire group, the median survival from brain metastases in patients without and with systemic treatment after WBRT was 3 and 10 months, respectively (P < .0001). In the triple-negative subset, the median survival from brain metastases with and without systemic treatment was 4 and 3 months (P = .16), and in the luminal A subset, it was 12 and 3 months, respectively (P = .003). In the luminal B subset, the median survival without further treatment, after chemotherapy and/or hormonal therapy, and after chemotherapy and/or hormonal therapy with targeted therapy was 2 months, 9 months, and 15 months, respectively (P < .0001). In the HER2 subset, the median survival was 4 months, 6 months, and 13 months, respectively (P < .0001). No significant response to systemic treatment was noted in the triple-negative breast cancer population.

Conclusions: Systemic therapy, ordered after WBRT, appears to improve survival in patients with the luminal A, luminal B, and HER2 breast cancer subtypes. Targeted therapy was found to have an additional positive impact on survival. In patients with triple-negative breast cancer, the role of systemic treatment after WBRT appears to be less clear, and therefore this issue requires further investigation.