Trastuzumab in metastatic breast cancer

Metastatic breast cancer is an incurable disease in a very high percentage of patients. Despite new progress in endocrine and other systemic therapies, this evidence remains challenging for patients and clinicians. HER2 protein is a member of the epidermal growth factor family of transmembrane receptors. HER2 is overexpressed in approximately 20% to 30% of breast cancers. Overexpression of HER2 has been shown to be associated with increased tumor proliferation and relative resistance to some types of chemotherapy and hormonal therapies. Trastuzumab, a humanized monoclonal antibody directed against HER2 protein, has been shown to be an efficacious and well tolerated treatment for HER2-overexpressing metastatic breast cancer, both as a single agent and when it is used in combination with chemotherapy.