Approximately 20% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2), providing an actionable target for many different therapies. In the metastatic setting, prognosis has improved greatly with the use of anti-HER2 drugs such as trastuzumab, pertuzumab, and trastuzumab-emtansine. In the third line setting and beyond, several emerging treatments have shown benefits, including novel small molecule targeted agents and antibody-drug conjugates. Systemic treatment of brain metastases in HER2-positive patients and the role of endocrine-based treatment for patients with hormone receptor (HR) positive disease remain areas of research interest. This article will review the current approach to systemic management of metastatic HER2-positive breast cancer in Canada, and present novel treatments that may be available in the near future.
Keywords: HER2; breast cancer; metastatic; neratinib; pertuzumab; trastuzumab; trastuzumab deruxtecan; trastuzumab emtansine; tucatinib.