ERBB2 and gastric cancer: Post hoc subgroup analysis in patients with prior trastuzumab use in ATTRACTION‐2 trial showed that patients with prior trastuzumab use, who were predicted to be HER2-positive cases with high probability, showed comparable, even better prognosis compared with patients who were not treated with trastuzumab [25], encouraging the induction of nivolumab as salvage-line treatment in HER2-positive gastric cancer.