Eligible patients had histologically confirmed esophageal, gastroesophageal junction, or gastric adenocarcinoma that was unresectable or metastatic, with HER2 amplification assessed by local pathology laboratory assessment (3 + by immunohistochemistry, or 2 + by immunohistochemistry with in situ hybridization with HER2/CEP17 ratio ≥2),. Here, ERBB2 is linked to gastric adenocarcinoma.