Adjuvant Trastuzumab for HER2-positive Early Breast Cancer: Efficacy, and Factors Affecting Survival

Breast cancer is a heterogenous disease. Gene expresssion studies have identified five distinct molecular subtypes of breast cancer. The use of gene expression profiling is currently limited in many clinical settings, and hence histopathological markers such as estrogen receptor (ER), progesterone receptor (PR), and HER2 are used as surrogates for the moleculer subtypes, which divide breast tumors into distinct phenotypes with distinct outcomes (Perou et al., 2000). The gene for the human epidermal growth factor receptor2 (HER2) encodes for a transmembrane tyrosine kinase receptor protein. HER2 has both prognostic and predictive importance for invasive breast cancer. In approximately 15-25% of patients with breast cancer, HER2 gene is amplified and is associated with increased