Abstract: Objective Compare the clinicopathological factors of microsatellite unstable(dMMR) and microsatellite stable(pMMR) in right colon cancer and analyze the factors affecting overall survival(OS) and disease-free survival(DFS) between the two groups.Methods Clinical data with right colon cancer of patients who underwent radical resection from January 1,2016 to December 31,2023 were retrospectively analyzed(a total of 247 patients were included,including 43 dMMR and 204 pMMR).Through propensity score matching,the baseline difference between the two groups was matched 1∶1,and a total of 86 cases were obtained,43 cases in dMMR and 43 cases in pMMR.The difference of relevant indicators between the two groups was analyzed,and univariate and multivariate Cox analysis was performed for OS and DFS.The survival curve was plotted, and the comparison of survival rates was conducted using the Log-rank test.Results According to age,location,tumor length,shape,histological type,T,N,TNM stage,nerve invasion,and differentiation degree with 1∶1 matching(P<0.05),there was no statistical difference in baseline data between dMMR and pMMR patients with right colon cancer(P>0.05).It was found that 5-year OS of dMMR patients with right colon cancer was significantly better than pMMR(P<0.05),and 5-year DFS dMMR was better than pMMR(P<0.05).Protective factors affecting OS of dMMR right colon cancer included tumor length<5cm,T₁-3,M₀,Stage Ⅰ-Ⅲ,absence of intravascular cancer thrombi and absence of nerve invasion(P<0.05).In survival analysis,M₀ was compared with M₁(95% vs. 60%,P<0.05).Stage Ⅰ-Ⅲ compared with stage Ⅳ(95% vs. 54%,P<0.05);No vascular cancer thrombus vs. cancer thrombus(94% vs.88%,P<0.05).Protective factors affecting DFS of dMMR right colon cancer included age < 50 years,no mucous or sig-ring cells,M₀,Stage Ⅰ-Ⅲ,and no intravascular cancer thrombus(P<0.05).In survival analysis,M₀ was compared with M₁(90% vs. 63%,P<0.05).Stage Ⅰ-Ⅲ compared with stage Ⅳ(92% vs. 57%,P<0.05);There was a significant difference between non-vascular cancer thrombus and vascular cancer thrombus(91%vs. 77%,P<0.05).Conclusion The patients with dMMR had higher OS and DFS than pMMR,which were not affected by clinical factors.

Key words: colon cancer, microsatellite instability, propensity score, overall survival, disease-free survival