Clinical Experience of Complete Pathological Response in MSI-H and PDL1 Positive Inoperable Gastric Cancer Treated with ICIs and Chemotherapy: Two Case Reports

Background: During last decades, Immunotherapy (IT) has become the gold standard treatment of many types of cancers.In gastrointestinal (GI) cancers, predictive factors of response to IT are high microsatellite instability (MSI-H) and programmed death ligand 1 (PDL1) expression.On the basis of the results from the phase 3 Checkmate 649, Nivolumab (anti-PD1) and chemotherapy (CT) is the new first line chemotherapy for advanced or metastatic gastric cancer (HER2-negative, PD-L1 CPS 5.Case summary: Herein, we describe two clinical cases of patients affected by advanced gastric cancer (HER2-negative, PD-L1 CPS 5, MSI-H), treated with immune checkpoint inhibitor (ICI) and CT who reached pathological complete response. Conclusion:MSI-H is a strong predictor of response to IT in GI cancers, also in the neoadjuvant/perioperative gastric cancer setting.We attend for confirmation by phase II infinity trial, maybe a non operative management is possible also for gastric cancer.