Trastuzumab (Herceptin, Roche, Basel, Switzerland) is a recombinant humanized monoclonal antibody that targets HER2, and a one-year period of administration of adjuvant trastuzumab has already been confirmed to be the standard of care in the treatment of patients with early-stage HER2-positive breast cancer.13 Trastuzumab-based chemotherapy has been given to HER2-positive AGC patients with promising clinical benefits and acceptable levels of toxicities. This evidence concerns the gene ERBB2 and breast cancer.