With the HELOISE trial failing to demonstrate a clinical benefit with higher dosing, trastuzumab at a loading dose of 8 mg/kg followed by 6 mg/kg maintenance dose every 3 weeks with chemotherapy (consistent with the ToGA trial) remains the standard of care for the first-line treatment of HER2-positive metastatic gastric or GEJ adenocarcinoma. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.