The treatment strategy for microsatellite instability-high (MSI-H) cases connected to genetic counseling in our hospital

Abstract

　Recently, microsatellite instability (MSI) tests have been widely used to identify MSI-high (MSI-H) among patients with various types of tumors. However, the incidence of these MSI-H cases, their prognosis, and rate at which patients are connected to genetic counseling have not yet been clarified. We report our experience with the treatment of MSI-H cases in our hospital. In this study, we investigated the results of MSI tests performed in clinical practice. A total of 203 patients were examined using MSI tests between April 2019 and December 2022. In all cancer cases (digestive, n=159; urinary, n=28; gynecological, n=12), the overall frequency of MSI-H was 5.4% (n=11). The original organs of the MSI-H tumors included the right-sided colon in five cases, the distal side of the stomach in five cases, and the prostate in one case. Only one patient with colon cancer received genomic counseling and was diagnosed with Lynch syndrome (with MLH-1 germline mutation). Immune checkpoint inhibitors (pembrolizumab) were used in 9 of the 11 MSI-H cases. There were no common clinical or histological characteristics in the MSI-H cases. Further studies are required.