Metformin Significantly Reduced Risk Of Colorectal Cancer In Type 2 Diabetes Patients:A Meta-analysis

Objective : To evaluate the association between metformin therapy and the risk of colorectal cancer in patient with type 2 diabetes.Methods:Pub Med, Embase, Medline, the cochrane library, China National Knowledge Infrastructure( CNKI), Wan Fang Digital Journal Full-text Database, and database for Chinese Technical Periodicals(VIP) were searched. Statistical analysis was performed by meta-analysis using Rev Man5.2 software.Results:A total of 16 original papers met the inclusion criteria, 12 of which were the cohort study papers including 14 subgroup studies with 666790 subjects and the other 4 of which were case-control studies with 32078 subjects. Meta-analysis of cohort studies showed that metformin therapy reduced colorectal cancer risk by 32% in type 2 diabetes patients compared to those with other oral glucose-lowering drugs(RR=0.68,95%CI 0.59~0.78,P<0.00001);According to the different of follow-up time, cohort studies were divide into two subgroups of less than or equal to five years and more than five years. Follow-up time less than or equal to five years group was found that metformin therapy reduced colorectal cancer risk by 28% in type2 diabetes patients(RR=0.72,95%CI 0.63~0.83,P<0.00001);Follow-up time more than five years group was found that metformin therapy reduced colorectal cancer risk by 37% in type 2diabetes patients(RR=0.63,95%CI 0.46~0.88,P<0.00001);According to regional difference subgroup analysis, it shows that there is similar reduction in risk of colorectal cancer by metformin therapy among patient with type 2 diabetes between Asian and Occident.(RR=0.68,95%CI 0.56~0.82,P<0.00001;RR=0.67,95%CI 0.51~0.86,P<0.00001).the results according to the case-control studies showed that metformin therapy may be associated with a reduced risk of colorectal cancer among patient with type 2 diabetes(OR=0.84,95%CI 0.73~0.95,P=0.008).Conclusion:Metformin therapy is likely to lower colorectal cancer risk in patient with type2 diabetes, and with the duration of treatment prolonging the preventive effect is more outstanding; there is similarity that metformin therapy reduced risk of colorectal cancer among patient with type 2 diabetes of Asian and Occident.