Systemic Treatment Options for HER2-Positive Breast Cancer Patients with Brain Metastases beyond Trastuzumab: A Literature Review

Background: The incidence of brain metastases (BM) in breast cancer patients has increased. Many retrospective analyses have shown that first-line treatment with trastuzumab prolongs survival in patients with HER2-positive BM. In contrast, the evidence for other therapies targeting HER2 for patients with BM is rare. Methods: The aim of this review is to update the reader about current systemic treatment options in patients with HER2-positive metastatic breast cancer with BM who had already received trastuzumab. A literature search was performed in the PubMed database in June 2016. 30 relevant reports concerning the efficacy of trastuzumab emtansine (T-DM1), lapatinib and its combination with other cytotoxic agents, pertuzumab and novel HER2-targeting substances were identified. Results: There is limited but promising evidence for the use of T-DM1 and pertuzumab in the treatment of BM. Up to now, most reported studies used lapatinib as treatment of HER2-positive breast cancer with BM, a treatment with only a modest effect and a high toxicity profile. The combination of lapatinib with cytotoxic agents seems to result in better response rates. Conclusion: Further prospective investigations are needed to investigate the efficacy of the established and novel HER2-targeting agents on BM in HER2-positive breast cancer patients.