The results of the RC48 phase-I study of treatment of HER2 low expressed GC indicated that the antitumor response of HER2 IHC2+/FISH- patients resembled that of IHC2+/FISH + and IHC3+ patients, with 72.7%, 60.0% and 52.6% of patients achieving significant cancer shrinkage, separately (Xu et al., 2021). This evidence concerns the gene ERBB2 and gastric cancer.