Metformin Prevent The Incidence Of Colorectal Tumor With Type 2diabetes Mellitus:a Meta-analysis

Objective: By collecting comprehensively the original data to evaluate the association between metformin therapy and the risk of colorectal tumor in patients with type 2 diabetes and provide the basis of the evidence-based medicine.Methods: Pubmed,Embase,the Cochrane Library,Wanfang database,China National Knowledge Infrastructure(CNKI),Chinese Biomedical Literature(CBM)and VIP database from inception to Oct.2016 were searched for the cohort studies in evaluating the effect of metformin on colorectal tumor in patients with type 2 diabetes.Two investigators identified and extracted data independently.In order to better understand the risk of bias among included studies,the Newcastle-Ottawa Scale was applied for quality assessment in observational studies,with a score≥7 indicative of high quality.A meta-analysis was performed using Rev Man 5.3 and Stata SE 12.0 software.Heterogeneity was estimated using Q and I2 with alpha values.Subgroup and sensitivity analyses were conducted to evaluate the robustness of the results.The risk of publication bias was assessed by examining funnel plot asymmetry as well as Begg test and Egger test.Results: A total of 17 original articles and 20 independent researches met the included criteria.Using the Newcastle-Ottawa scale quality tool,the quality of included studies was moderate or high.Meta analysis showed that metformin therapy reduced the risk of colorectal tumor by 15% in type 2 diabetes compared with other oral glucose-lowering drugs(RR = 0.85,95% CI: 0.80 0.91,P < 0.00001),and reduced the risk of colorectal cancer by 13%(RR = 0.87,95% CI: 0.81 0.93,P < 0.0001)as well as reduced the risk of colorectal adenomas by 24%(RR = 0.76,95% CI: 0.66 0.86,P < 0.0001).There was considerable heterogeneity among studies(Q test P = 0.005;I2 = 51%).The subgroup analyses result had no heterogeneity(Q test P = 0.03;I2 = 47%)in western people,and had no heterogeneity(Q test P = 0.50;I2 = 0%)the eastern people.But two groups of test(Q test P = 0.005;I2 = 87.6%)existed severely heterogeneity,therefore the heterogeneous source was mainly caused by the eastern and western study population.By the random and inherent effect model merged respectively statistic,the results were steady,this researched conclusion was trusted.There was a possible publication bias among studies based on the Begg test or Egger test and visual inspection of the funnel figure.Conclusion: The current study data supported that metformin can reduce the risk of the incidence of colorectal tumor in type 2 diabetes,and can be applied to the primary prevention of colorectal tumor in type 2 diabetes.