Systemic treatment of HER2-positive metastatic breast cancer: A systematic review

Aim: We aimed to systematically review and summarize data from the available clinical trials that examined the treatment of HER2-positive metastatic breast cancer. Methods: We reviewed phase 2 and 3 studies in which an anti-HER2 agent was used in one or both arms of the study. While formal meta-analysis was not possible for such a heterogeneous group of trials, resulting forest plots outline some generalizable findings. Results: There is strong evidence that the addition of an anti-HER2 agent to standard chemo- or endocrine therapy improves clinically relevant measurable outcomes. There is also consistent evidence that initial treatment with trastuzumab alone (and subsequent use of a cytotoxic) is inferior to the initial combination of trastuzumab plus chemotherapy, and that either T-DM1 or dual anti-HER2 agents are superior to single anti-HER2 agent regimens. There is no strong evidence that the use of more than one cytotoxic agent together with an anti-HER2 agent confers any benefit over a single cytotoxic, anti-HER2 combination. Conclusion: This review provides a strong evidence base for current clinical practice with a discussion of treatment in the Australian setting.