When HER2 is not the target: advances in the treatment of HER2-negative metastatic breast cancer

The anti-human epidermal growth factor receptor 2 (HER2) agent trastuzumab has improved outcomes in breast cancer patients with HER2 over-expressing tumours. However, systemic treatment for patients with HER2-negative disease is still limited to endocrine and cytotoxic therapies. The increasing use of the anthracyclines and taxanes in early stage disease has reduced the available therapeutic options for patients with relapsed disease, and choices are further limited for patients with triple-negative tumours, who typically have a poor prognosis. The novel agents bevacizumab and ixabepilone were recently approved for metastatic breast cancer, and numerous other agents are currently in clinical development that may contribute further valuable therapeutic options.