It is strongly recommended to evaluate the expression statuses of HER2, PD-L1 combined positive score (CPS), microsatellite instability (MSI), and claudin 18.2 prior to first-line chemotherapy in patients with unresectable esophagogastric junction adenocarcinoma: (result of voting: 90% [44/49]; strength of evidence: C). This evidence concerns the gene CD274 and gastroesophageal junction adenocarcinoma.