Prognostic value of human epidermal growth factor receptor 2 status and systemic therapy in breast cancer with brain metastases treated with radiotherapy

Purpose To evaluate the prognostic value of human epidermal growth factor receptor 2 (HER2) status and how to use HER2-targeted therapy in breast cancer (BC) with brain metastases (BM) treated with radiotherapy. Methods We retrospectively reviewed the data of 103 BC patients with parenchymal BM treated with radiotherapy. We collected data on the hormone receptor (HR), HER-2 amplification status, and systemic therapy after treatment for BM. The primary outcome was overall survival (OS), which was calculated from the diagnosis of BM to death. Results The median follow-up time from the diagnosis of the first BM was 9.1 months (range, .7-88 months). The 2-year OS of the HR-positive and HER2-positive (HR+HER2+) BC (31.3 mo) was significantly better than those of the HR-HER2+ (9,5 mo, p=.002), HR+HER2- (9.9mo, p=.003), and triple-negative BC (3.9 mo, p<.001) ( . Of the 36 HER2-positive patients, 31 patients treated with HER2-targeted therapy after radiotherapy for BM had a significantly better 2-year OS than those who did not receive HER2-targeted therapy (43% vs. 0%; p < .001). Among the 31 patients treated with HER2-targeted therapy, the 2-year OS for those treated with multiple anti-HER2 agents during the entire course of treatment was significantly higher than that for patients treated with a single agent (60% vs. 24%; p = .006). Conclusions HR+HER2+ BC patients with BM treated with radiotherapy show a better prognosis than other subtypes. For HER2-positive patients with good prognosis, it may be important to continue HER2-targeted therapy appropriately after radiotherapy for BM.