Association of activin type II receptor mutation with microsatellite instability in gastric cancer.

Abstract

e23191 Background: Microsatellite instability-high status (MSI-H) and alterations in the DNA mismatch repair pathway associate with the efficacy of 5-FU and immune checkpoint inhibitors in patients with gastrointestinal cancers. The activin type II receptor (ACVR2) that binds to the transforming growth factor beta superfamily of ligands is frequently mutated in MSI-H colorectal cancer. However, the incidence of ACVR2 mutations in gastric cancer patients remains unclear. The aim of this study is to reveal the incidence and to examine the association between the MSI-H and ACVR2A mutations in gastric cancer patients. Methods: 124 archived FFPE gastric cancer tissues (stage I-IV), who were operated at Niigata University Medical and Dental Hospital or Niigata Cancer Center Hospital, were analyzed for ACVR2A mutation and MSI status with the NGS-based comprehensive genomic test platform. Clinicopathological characteristics of the patients were also examined. Results: All 124 gastric cancer patients were successfully analyzed. 13 out of 124 patients (10.4%) showed MSI-H status. Interestingly, 10 of 13 MSI-H patients (76.9%) showed ACVR2A mutation, where none (0%) was found among patients with microsatellite stable status (P < 0.001), indicating the strong association between ACVR2A mutation and MSI status in gastric cancer patients. In the ACVR2A mutated group, there was a female predominance (P < 0.05), and cancers of the lower part of the stomach were more common (P < 0.05), compared with the wild type group. Only one of 10 patients with ACVR2A mutation died, and the patients with ACVR2A mutation show a 5-year overall survival rate of 90%. No statistically significant difference in survival was achieved between patients with ACVR2A mutation and wild type; this is probably due to the small number of patients. Conclusions: 10 of 13 MSI-H patients showed ACVR2A mutation. Our results indicate a strong association between ACVR2A mutation and MSI-H in gastric cancer patients.