Targeting signal transduction pathways in metastatic breast cancer: a comprehensive review.

Greater understanding of the underlying etiology and biology of breast cancer is enabling the clinical development of targeted therapies for metastatic breast cancer (MBC). Following the successful introduction of trastuzumab, the first human epidermal growth factor receptor (HER) biologically targeted therapy to become widely used in MBC patients, other agents have been developed. Novel agents include monoclonal antibodies such as pertuzumab, which bind to receptors on the cell surface, and tyrosine kinase inhibitors (TKIs) such as lapatinib, which target intracellular pathways such as that of the epidermal growth factor receptor.