HER2 status and breast cancer therapy: recent advances

The phenotype imparted by expression of the HER2 gene in breast cancer and progress made in modifying the disease's natural history through pharmacologically modulating its function has served as a paradigm for rationally targeted therapy and personalized medicine. About 20-25% of breast cancer cases are associated with HER2 gene amplification and overexpression, creating a distinct subtype of breast cancer that is associated with more aggressive behaviour, higher likelihood of overall and brain metastases, and differential responsiveness to certain hormonal and chemotherapeutic agents. Anti-HER2 monoclonal antibodies have led to significant improvements in survival for both advanced and early stage HER2+ breast cancer, while newer agents, including other antibodies and HER2 receptor tyrosine kinase inhibitors and signal transduction modulators, are also demonstrating clinical activity and represent further opportunities to improve curability and quality of life.