Objective:To investigate the efficacy of integrated Chinese and Western medicine (IM) in the treatment of metastatic colorectal cancer (mCRC) in a cohort study.Methods:The survival outcome of patients receiving IM was compared with that of patients receiving Westem medicine alone.The study design was adopted with “continuous administration of Chinese medicine for ≥ 3 months” as the exposure factor.Patients who met this exposure factor were assigned to the IM cohort (Group A,110 patients).Patients who did not meet this exposure factor were assigned to the Westem medicine cohort (Group B,225 patients).The overall survival (OS),progression-free survival (PFS),and 1st year,2nd year,and 3rd year survival in the two cohorts were compared.Results:The median OS in Group A and B were 18 months [95％ confidence interval (CI) 15-21] and 16 months (95％ CI 14-18),respectively,and the median PFS in Group A and B were 6 months (95％ CI 4-7) and 5 months (95％ CI 4-6),respectively.No statistically significent differences were observed between the groups (P=0.186,P=0.223).Group A demonstrated significantly longer OS and PFS than Group B in the following subgroups:female patients,patients with lesions in the right half of the colon,and those who received first-line treatment (P＜0.05).In the subgroup of elderly patients (age＞65 years),the OS in Group A was longer than that in Group B (P＜0.05).Conclusion:IM could prolong the survival of patients with mCRC.(Registry No.ChiCTR-IOR-17010497)