Trastuzumab, in combination with capecitabine and cisplatin or 5‐FU and cisplatin, significantly improved survival in patients with overexpression of HER2 18 (Table 1), but only 20% of gastric cancers and 30% of gastroesophageal cancers overexpress HER2 19. This evidence concerns the gene ERBB2 and gastric cancer.