Background: With the more effective control of visceral metastases in patients with metastatic breast cancer (MBC), an increasing number of patients face brain metastases (BM). The aim of this retrospective analysis was to investigate the incidence and factors affecting the prognosis of patients with BM under trastuzumab treatment for MBC. Patients and Methods: A total of 75 HER2positive patients treated with trastuzumab for MBC were included. Results are discussed in the context of the current literature. Results: Patients who developed BM (n = 29) had longer median progression-free survival (PFS) during first-line chemotherapy and longer overall survival (OS) after diagnosis of MBC than 46 patients without BM (PFS: 27 vs. 14 months, p = 0.039; OS: 46 vs. 18 months, p = 0.067). Median survival of patients with continuation of trastuzumab after diagnosis of BM was longer than survival of patients with discontinuation of trastuzumab treatment after BM (18 vs. 3 months, p = 0.006). Survival of patients who were treated with surgery and radiotherapy for BM was better compared with radiotherapy alone (9 vs. 5 months, p = not significant) or best supportive care (9 vs. 2 months, p = 0.049). Conclusions: Continuation of trastuzumab treatment as well as resection of BM seem to give further benefit in the treatment of patients with HER2-overexpressing MBC.
