Initially, the ToGA trial included only patients with HER2 IHC 3+ or HER2 FISH+ (HER2/CEP17 ratio of ≥2) advanced gastric cancer, but the post-hoc subgroup analysis of the trial showed that trastuzumab treatment was more beneficial to HER2 IHC 3+ or IHC 2+/FISH+ groups [11]. This evidence concerns the gene ERBB2 and gastric cancer.