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Advanced (locally advanced, non-operable, and/or metastatic) gastric (G) or gastro-esophageal junction (GEJ) adenocarcinomas are cancers with a poor prognosis, with a 5-year survival rate of 30%. Several therapeutic innovations have recently been developed, leading to an increase in overall survival. Analysis of tumor tissue for HER2 overexpression, PD-L1 CPS score, and microsatellite instability (dMMR/MSI) is now essential to guide therapeutic management. The search for overexpression of the claudin 18.2 protein is set to join this list of criteria, following the positive results of phase III trials evaluating a specific antibody (zolbetuximab) in cases of protein overexpression. In addition to these innovative therapies, chemotherapy has also undergone a major shift, in the wake of the positive results of the GASTFOX-PRODIGE 51 study, which now allows for the possibility of offering an intensified regimen combining 5-FU, oxaliplatin, and docetaxel (TFOX regimen) in selected cases.