CD274 and esophageal adenocarcinoma: HCRN GI17-319 was a multicenter, single-arm, phase II clinical trial with a prespecified 6-subject safety run-in of the anti-PD-L1 antibody avelumab, combined with trastuzumab and mFOLFOX6, in previously untreated, metastatic, HER2-amplified gastric and esophageal adenocarcinomas.