Abstract: Objective：Based on SEER database,to explore the effect of primary tumor resection on the prognosis of patients with liver metastases from colorectal cancer(CRLM) who are not feasible to remove metastases and to analysis the related factors of prognosis.Methods：Collecting the clinical and prognostic data of patients with colorectal cancer liver metastases between 2010 and 2015 from the SEER database.According to the criteria,about 3,920 cases of highvalue clinical data were finally obtained,including 3232 patients in the chemotherapy combined primary resection group(combination group) and 688 patients in the systemic chemotherapy alone group(chemotherapy group).Propensity score matching(PSM) method was used to balance the clinicopathological baseline characteristics of the two groups of patients,and the overall survival rate(OS) and cancerspecific survival rate(CSS) difference between the two groups of patients were compared.Analysis of risk factors for prognosis of patients in the combined group.Results：Before matching through PSM,the OS and CSS in the combination group were significantly higher than those in the chemotherapy group(P＜0.05),but the clinicopathological characteristics of the two groups showed significant imbalance,such as gender,tumor grade,tumor site,tumor size,race,marital status,T stage,N stage and CEA.After matching through PSM,1168 patients were finally effectively screened,including 584 patients in the combination group and chemotherapy group.The differences in clinical pathological characteristics of the two groups were significantly reduced,the baseline distribution characteristics were significantly improved(P>0.05),including gender,tumor grade,tumor size,race,marital status,and CEA.The OS and CSS of the combined group were still significantly higher than those of the chemotherapy group(P＜0.05).After analyzing of the COX risk regression model,it was found that age,tumor location,tumor N stage,radiotherapy,and marital status were independent risk factors that affected the prognosis of patients in the combined group.Conclusion：For the CRLM patients who are not feasible to remove metastases,a treatment strategy based on systemic chemotherapy combined with primary resection should be adopted.

Key words: colorectal cancer, 〓liver metastasis, 〓propensity score matching, 〓prognosis