The ToGA trial showed that in patients with advanced HER2-positive GC, trastuzumab combined with platinum-based chemotherapy increased median overall survival to 13.8 versus 11.1 months with chemotherapy alone.13 HER2 testing thus became the first predictive biomarker for GC.98 Assessment of HER2 expression in GC is complex and requires specific training. Here, ERBB2 is linked to gastric cancer.