Relationship Between Microsatellite Instability Of Gastric Cancer And Efficacy Of 5-FU Based Adjuvant Chemotherapy

Objective: Compared with Microsatellite stability/Low-frequency Microsatellite instability(MSS/MSI-L)patients with gastric cancer,High-frequency microsatellite instability(MSI-H)patients with surgery have better survival benefits.However,after fluorouracil(5-FU)based adjuvant chemotherapy,there is no strong evidence for the survival difference between MSI-H patients and MSS/MSI-L patients.The purpose of this study is to explore the difference of prognosis of patients with different microsatellite instability(MSI)status after 5-FU based adjuvant chemotherapy by retrieving relevant studies for meta-analysis and conducting a prospective cohort study of gastric cancer patients receiving 5-FU based adjuvant chemotherapy.Methods: The study was divided into two parts.The first part is meta-analysis,in this part,meta analysis was carried out by retrieving the relevant randomized controlled trials(RCT)studies published from 2009 to 2017.Meta-analysis was carried out by statistical and summary of Hazard ratio(HR)value and 95% Confidence interval(CI)of Overall survival(OS)in MSI-H group and MSS/MSI-L group.The second part is the prospective cohort study,which collects patients with gastric cancer receiving 5-FU based adjuvant chemotherapy after radical gastrectomy from January 2017 to March 2020 in 2 hospitals.The patients were divided into two groups: MSS/MSI-L and MSI-H group.The patients were followed up for 1 and 2 years disease-free survival(DFS)rate.Results: 4 RCT studies were included in meta-analysis.The results showed that there was no significant difference in OS between MSS/MSI-L and MSI-H patients(HR = 1.90,95% CI 0.91-3.93,P = 0.08),which suggested that different MSI status may had no predictive effect on OS of gastric cancer patients receiving 5-FU-based adjuvant chemotherapy.In prospective cohort study,the median follow-up time was 22 months,the results showed that the 1 and 2 years DFS rates of MSS/MSI-L group were 95.4% and 88.6%,respectively,and the 1 and 2 years DFS rates of MSI-H group were 98.2% and 89.0%,respectively,P = 0.85,suggesting that there was no significant difference between MSS/MSI-L and MSI-H patients in 1 and 2 years DFS rate.Conclusion: The prognosis of MSS/MSI-L and MSI-H patients with gastric cancer after 5-FU-based adjuvant chemotherapy may not be different.