The first-time data from the Phase III KEYNOTE-811 trial, evaluating pembrolizumab in combination with trastuzumab plus chemotherapy for metastatic HER2+ gastric or GEJ adenocarcinomas, demonstrates a meaningful improvement in ORR compared with the standard combination of chemotherapy (74% vs. 52%, respectively; p = 0.00006) resulting in a Food and Drug Administration (FDA) approval for Her2+ patients [3]. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.