A Review of Trastuzumab-Based Therapy in Patients with HER2-positive Metastatic Breast Cancer

The ERBB2 or HER2 receptor is overexpressed in 25% of breast cancers and is associated with poor prognosis. Trastuzumab, a monoclonal antibody targeting HER2 has been demonstrated to improve survival when combined with chemotherapy for the treatment of HER2 overexpressing metastatic breast cancer (MBC). Further studies have endeavoured to clarify the optimum chemotherapy regimen in combination with trastuzumab for MBC and its use together with novel biological agents. This review summarises these data together with preclinical studies exploring the mechanism of trastuzumab action and causes of drug resistance. The frequent incidence of brain metastases in patients on trastuzumab is highlighted, and data on the continuation of trastuzumab following CNS and non-CNS progression reviewed.