Abstract 616: Literature review and meta-analyses of the prevalence of microsatellite instability high (MSI-H) and deficient mismatch repair (dMMR) for colorectal (CRC), gastric (GC), endometrial (EC) and ovarian cancers (OC) in Chinese population

Purpose Given the high prevalence of MSI-H/dMMR in gastrointestinal and gynecologic cancers we systematically collected published studies and investigated its’ prevalence for Chinese CRC, GC, EC, OC subjects to better understand the size of potential target population available for pembrolizumab treatment in China. Experimental Design Both Chinese and English literature were searched in WanFang and PubMed database respectively. Studies were included if they assessed prevalence of MSI-H by PCR based method investigating 5 markers from NCI or Promega panel, and/or dMMR by immunohistochemistry (IHC) for all 4 MMR proteins. Studies focusing only on hereditary or sporadic cancer were filtered out. Among eligible studies, meta-analyses (DerSimonian Laird random effect model) were performed on the proportion of MSI-H/dMMR for each tumor type by R metafor package. Prevalence for advanced stage (III/IV) were also extracted if the data were available. Results For CRC, the prevalence of MSI-H estimated from 11 studies (13.7% [10.2-17.6%]) was similar as that of dMMR from 22 studies (14.6% [12.3-17.1%]). Pooled prevalence of MSI-H/dMMR from 32 studies (12,341 subjects) was estimated at 14.1% (12.2-16.1%), and 9.7% (7.2-12.5%) from 17 studies (3,933 subjects) for advanced stage CRC. The prevalence estimation for GC, EC and OC were 18.5%, 26% and 12.9% respectively. Further, the prevalence in advanced stage cancer, regardless of the cancer type, tended to be numerically lower than the all-stage combined prevalence. Conclusions This was the first study comprehensively integrating published studies to estimate prevalence of MSI-H/dMMR across 4 main tumor types for Chinese subjects. The meta-analysis indicated the prevalence of MSI-H/dMMR for all or advanced stage Chinese cancer patients might be similar as that for western population. Citation Format: Xiaoqiao Liu, Jiaqi Fan, Kai-Li Liaw, Mo Xu, Yu Zhou, Mayur Amonkar, Gefei Zeng. Literature review and meta-analyses of the prevalence of microsatellite instability high (MSI-H) and deficient mismatch repair (dMMR) for colorectal (CRC), gastric (GC), endometrial (EC) and ovarian cancers (OC) in Chinese population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 616.