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

The content of this article has been reviewed by independent peer reviewers to ensure that it is balanced, objective, and free from commercial bias. No financial relationships relevant to the content of this article have been disclosed by the authors or independent peer reviewers. Greater understanding of the underlying etiology and biology of breast cancer is enabling the clinical develop-ment of targeted therapies for metastatic breast cancer (MBC). Following the successful introduction of trastu-zumab, the first human epidermal growth factor recep-tor (HER) biologically targeted therapy to become widely used in MBC patients, other agents have been de-veloped. 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 a