Abstract 4316: Frequent microsatellite instability in Chinese solid tumor patients

Abstract

Abstract Background Microsatellite instability (MSI) has important clinical implications related to therapeutic options and prognostic assessment. Few studies have been done on the frequency of MSI in cancers and the correlation between microsatellite status and clinicopathological features in Chinese solid tumor patients. Methods A total of 10149 Chinese solid tumor patients were collected for genome testing using a targeted next-generation sequencing (NGS) panel (OrigiMed, Shanghai). Microsatellite status and other clinicopathological features were examined. Fisher's exact test was used for statistical analysis. Results MSI-high (MSI-H) was observed in 188 solid tumors (1.8%). Cancer subtypes with significantly higher MSI frequencies included colorectal adenocarcinoma (8.4%), gastric adenocarcinoma (6.9%) and intrahepatic cholangiocarcinoma (2.7%). No statistical significant difference was found in the proportion of MSI in women and men (1.9 % vs 1.7%, respectively). The proportion MSI tumors was higher in older patients (1.3% at 60-69 years, 2.8% at 70-79 years,P<0.0001) and younger patients (1.4% at 50-59 years, 3.0% at 40-49 years, P<0.0001). Compared with microsatellite stable (MSS) carcinomas, MSI was significantly correlated with the oldest and youngest age ranges that were tested, tumors found in the stomach and intestine, and in colorectal adenocarcinoma and gastric adenocarcinoma subtypes. In addition, 123 of the 188 samples (65.4%) harbored at least one MMR gene mutations predicted as loss of functions, including nonsense mutations or truncations in MSH2, MSH6 or MLH1. 2.3% (217/9354) MMR gene mutation was detected in MSS samples (p<0.0001). Conclusions This study revealed MSI-H in approximately 1.8% of Chinese solid tumor patients and a significant association between MSI-H and MMR gene mutations. These results suggest that there are specific tumor types and clinicopathological features associated with a higher frequency of MSI, indicating a bias during tumorigenesis. Also, these results may potentially contribute to more effective treatment options and a better prognostic assessment for solid tumor patients. Citation Format: Huilin Wang, Jiang Zhu, Guanbiao Liang, Yongyong Wang, Jianji Guo, Min Zheng, Qin Fu, Weiwei Shi. Frequent microsatellite instability in Chinese solid tumor patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4316.