New approaches for human epidermal growth factor receptor 2-low and human epidermal growth factor receptor 2-overexpressing metastatic breast cancer

Purpose of review In recent years, there has been a flurry of activity in the human epidermal growth factor receptor 2 (HER2)positive metastatic breast cancer space. New, powerful drugs like trastuzumab deruxtecan have challenged our fundamental definition of what HER2 expression means as a predictive biomarker. Recent findings Recent approvals of multiple agents in the second line-metastatic setting have given patients access to a variety of new agents, but also raise questions with regard to optimal sequencing. Summary This review will explore current issues with HER2 testing, recently approved drugs in the HER2+ and HER2 low spaces, as well as novel agents/combinations on the horizon.