The phase-III ToGA trial demonstrated the benefit of the anti-HER2 mAb trastuzumab in combination with platinum-fluoropyrimidine chemotherapy (CHT) in patients with advanced GC, especially in a subgroup with HER-2 positivity, which was identified later on in a post hoc analysis as a HER2 IHC score 3+ alone or HER2 IHC 2+ and FISH positivity [15,27]. Here, ERBB2 is linked to gastric cancer.