[Microsatellite Instability in Gastric Cancer].

ABSTRACT

INTRODUCTION: Pembrolizumab and nivolumab are anti-programmed death receptor-1(PD-1)antibodies. The use of pembrolizumab for unresectable or metastatic cancer with microsatellite instability-high(MSI-High)has been recently approved. However, there were few clinical reports on MSI in gastric cancer. MATERIALS AND METHODS: We examined the clinicopathological features and MSI for 37 patients who underwent chemotherapy for unresectable gastric cancer in January 2019. RESULTS: MSI-High was observed in 3 patients(8.1%). Among the MSI-High patients, there was a tendency towards older age, female sex, undifferentiated type, distal-located lesions and lymphatic vessel invasions, but the differences were not significant. Eleven patients underwent chemotherapy with nivolumab, 4 of them had partial response(PR). Three out of the 4 patients (75%)were MSI-High. CONCLUSIONS: These results suggested that anti-PD-1 antibody could be effective as a secondary treatment for unresectable or metastatic gastric cancer among MSI-High patients.