Microsatellite instability and immunotherapy in gastric cancer: a narrative review

Abstract

Background and Objective: Immunotherapy is now a new treatment approach that is widespreadly accepted in the clinical practice, but the role in gastric cancer is still poorly elaborated. As mentioned in The Cancer Genome Atlas (TCGA) and Asian Cancer Research Group (ACRG) cancer classifications, the separate microsatellite instable (MSI) entirety is defined as a specific subtype of gastric cancer. In particular, the MSI hypermutator phenotype gastric cancer triggers immune response, allowing the specific molecular subset as a potential candidate for immunotherapy. The current review is to provide an updated overview of the available literature on the clinical implications of MSI in gastric cancer. Methods: We performed an extensive literature research on PubMed regarding the molecular, immunotherapy, and prognostic characteristics of MSI in gastric cancer, selecting only English-language articles from January 11, 2017 to August 12, 2022. Key Content and Findings: The complexity of gastric cancer puts forward higher demands for novel molecular-based individual therapeutics. MSI gastric cancers take up a relatively small patients population, and show distinctive clinicopathological features. MSI is significantly correlated with the response to immunotherapy in gastric cancer. The MSI cancers treated with immune checkpoint inhibitors show a favorable prognosis and MSI may serve as a biomarker for immunotherapy of gastric cancer. Conclusions: MSI detection plays a promising role in guiding the immunotherapy of gastric cancer. However, this still needs to be further verified in larger prospective clinical trials.