Metformin as a risk factor of pathogenesis of colorectal cancer in type 2 diabetes patients: a Meta-analysis

Objective　To evaluate the association between metformin therapy and the risk of pathogenesis of colorectal cancer in patients with type 2 diabetes. Methods　PubMed, Embase, Medline, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Digital Journal Full-text Database, and database for Chinese Technical Periodicals (VIP) till Nov. 2014 were searched for the cohort studies and case-control studies in evaluating the effect of metformin on colorectal cancer. A meta-analysis was performed using Rev Man5.2 software. The quality assessment of included studies was evaluated according to the Newcastle-Ottawa scale (NOS). Results　A total of 11 original articles met the inclusion criteria, 8 of them were articles withcohort studies including 12 subgroup studies with 447 234 subjects, and the other 3 case-control studies with 24 032 subjects. Metaanalysis of cohort studies showed that metformin therapy reduced the risk of pathogenesis of colorectal cancer by 30% in type 2 diabetes patients compared with those with other oral glucose-lowering drugs (RR=0.70, 95%CI: 0.58-0.85, P=0.0002). The results from the case-control studies showed that metformin therapy may be associated with a reduced risk of colorectal cancer in patients with type 2 diabetes (OR=0.78, 95%CI: 0.71-0.86, P<0.00001). Conclusion　Metformin therapy can lower the risk of pathogenesis of colorectal cancer in patients with type 2 diabetes. DOI: 10.11855/j.issn.0577-7402.2015.07.14