Immune checkpoint inhibitors (ICIs) in gastric or esophageal junction (JOG) adenocarcinoma with microsatellite instability (MSI)

In combination with chemotherapy, ICIs improve overall survival in patients with metastatic JOG or gastric adenocarcinoma by around 3 months, if the combined positive score (CPS) is increased. Another factor predictive of ICIs efficacy in this cancer is the existence of microsatellite instability (10% of localized forms and 5% of metastatic forms). As in colorectal cancer, in the case of MSI tumors, the efficacy of ICI is significant. In this cancer, studies have not been conducted on a selected MSI population, and in sub-group analyses have shown a major efficacy of ICI, insufficient to obtain marketing authorization for MSI indications. In the neo-adjuvant setting, two Phase 2 pilot studies evaluating ICI showed histological complete response rates of 60%, opening the door to studies aimed at organ conversation.