Genomic landscape of microsatellite instability in Chinese tumors: A comparison of Chinese and TCGA cohorts

Microsatellite instability (MSI) is an important biomarker for predicting the response to immunotherapy and prognosis that mainly results from a defective DNA mismatch repair (MMR) system and strongly correlates with high tumor mutation burden (TMB). Herein, we developed a novel method that integrates MSI score, MMR mutation status and TMB level to identify MSI status from next‐generation sequencing (NGS) data. The novel method displays a sensitivity of 96.80%, a specificity of 99.96% and an overall accuracy of 99.89%, compared to current standards. Using our novel method, we analyzed 11 395 Chinese patients across 30 cancer types. High microsatellite instability (MSI‐H) was detected in 210 (1.84%) samples in 18 of 30 cancer types assessed. Mutations in ACVR2A (73%), KMT2D (68%), KMT2B (66%) and MMR‐related genes (MLH1, MSH2, MSH6 and PMS2) were enriched in MSI‐H samples. Furthermore, MSI‐H samples were more likely to have high TMB (P