HER2 as a predictor of therapeutic response in breast cancer

HER2 gene encodes a 185 KD protein, which belongs to transmembrane type I tyrosine kinase receptor family that includes the EGF receptor, HER3, and HER4 [1]. Amplification of HER2 is associated with poor survival for patients with node positive breast cancer, and HER2 is a recognized prognostic marker [2,3]. Over the past 10 years, others and we have shown that HER2 may also serve to direct the selection of optimal adjuvant chemotherapy [4–8]. Although the mechanism is not understood, overexpression or gene amplification of HER2 (which we will refer to as HER2 positive or HER2 for the sake of brevity in this review) have been correlated with differential response to systemic therapy for breast cancer especially for doxorubicin. In this article, we will critically review the studies that provide evidence for the role of HER2 as predictor of response to chemotherapy.