ERBB2 and gastric cancer: The phase 3 ToGA study demonstrated the clinical benefits of trastuzumab combined with chemotherapy in patients with previously untreated, unresectable or metastatic HER2-positive (HER2 +) GC or GEJ cancer [6], and HER2-targeted combined chemotherapy has become the first-line treatment for HER2-positive advanced GC [7, 8].