Trastuzumab, a recombinant humanised IgG1k monoclonal antibody directed against the HER-2 extracellular domain, has shown a survival advantage in patients with metastatic HER-2-overexpressing gastric cancer [7]–[10], providing significant benefits in terms of response rate, median progression-free survival and overall survival [11]. This evidence concerns the gene ERBB2 and gastric cancer.