title: Metformin therapy and risk of colorectal adenomas and colorectal cancer in type 2 diabetes mellitus patients: A systematic review and meta-analysis.
abstract: Recent evidence indicates that metformin therapy may be associated with a decreased colorectal adenoma/colorectal cancer risk in type 2 diabetes patients. However, results are not consistent. We therefore performed a systematic review and meta-analysis to assess the association between metformin therapy and risk of colorectal adenomas/colorectal cancer in type 2 diabetes mellitus patients. We searched the literature published before Aug 31, 2016 in four databases: PubMed, Embase database, CNKI and VIP Library of Chinese Journal. Summary risk estimates (adjusted OR/adjusted RR/adjusted HR) with their 95% confidence interval (95% CI) were obtained using a random effects model. Twenty studies (including 12 cohort studies, 7 case-control studies and 1 randomized controlled trial study) were selected in terms of data of colorectal adenomas or colorectal cancer incidence. Metformin therapy was found to be associated with a decreased incidence of colorectal adenomas (unadjusted OR=0.80, 95% CI: 0.71-0.90, p=0.0002). When the adjusted data were analyzed, the summary estimate decreased to 25% reduction in colorectal adenomas risk (adjusted OR=0.75, 95% CI: 0.59-0.97, p=0.03). Besides, a significant reduction of colorectal cancer risk was also observed (unadjusted OR=0.73, 95% CI: 0.62-0.86, p=0.0002). And when the adjusted data were analyzed, colorectal cancer risk for metformin users was decreased with a reduction of 22%, compared with non-metformin users and other treatment users (adjusted OR=0.78, 95% CI: 0.70-0.87, p<0.00001). Our meta-analysis suggested that metformin therapy may be associated with a decreased risk of colorectal adenomas and colorectal cancer in type 2 diabetes mellitus patients.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University, Wuhan, 430071, China.|Global Health Institute, Wuhan University, Wuhan, 430071, China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Liu
authors.affiliation: Global Health Research Center, Duke Kunshan university, Kunshan, Jiangsu, 215316, China.
authors.forename: Lijing
authors.initials: L
authors.lastname: Yan
authors.affiliation: Global Health Research Center, Duke Kunshan university, Kunshan, Jiangsu, 215316, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Environmental Health Laboratory, Department of Public Health Sciences, University Hawaii at Manoa, Honolulu, HI 96822 USA.
authors.forename: Yuanan
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University, Wuhan, 430071, China.|Global Health Institute, Wuhan University, Wuhan, 430071, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Chu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University, Wuhan, 430071, China.|Global Health Institute, Wuhan University, Wuhan, 430071, China.
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University, Wuhan, 430071, China.|Global Health Institute, Wuhan University, Wuhan, 430071, China.
authors.forename: Yisi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department Of Public Health, Medicial College Shihezi University, Shihezi city, 832000, China.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Rui
authors.affiliation: Department of Epidemiology and Biostatistics and MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
authors.forename: Shaofa
authors.initials: S
authors.lastname: Nie
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University, Wuhan, 430071, China.|Global Health Institute, Wuhan University, Wuhan, 430071, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Xiang
mesh_terms: D000236:Adenoma / Q000517:prevention & control*; D015179:Colorectal Neoplasms / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D006801:Humans; D008687:Metformin / Q000627:therapeutic use*
chemical_list: D008687:Metformin
keywords: colorectal adenomas; colorectal cancer; meta-analysis; metformin; type 2 diabetes mellitus