title: Metformin therapy and the risk of colorectal adenoma in patients with type 2 diabetes: A meta-analysis.
abstract: BACKGROUND
  Existing data evaluating the impact of metformin on the colorectal adenoma (CRA) risk in patients suffering from type 2 diabetes (T2D) are limited and controversial. We therefore summarized the studies currently available and assessed the relationship between metformin treatment and risk of CRA in T2D patients.
  
  
  METHODS
  We systematically searched databases for eligible studies that explored the impact of metformin treatment on the occurrence of CRA in T2D patients from inception to June 2016. The summary odds ratio (OR) estimates with their 95% confidence interval (CI) were derived using random-effect, generic inverse variance methods. Sensitivity analysis and subgroup analysis were performed.
  
  
  RESULTS
  Seven studies involving 7178 participants met the inclusion criteria. The pooling showed that metformin therapy has a 27% decrease in the CRA risk (OR, 0.73; 95% CI, 0.58 - 0.90). In subgroup analysis, we detected that metformin exhibits significant chemoprevention effects in Asia region (OR, 0.68; 95% CI, 0.48 - 0.96). Similar results were identified in both studies with adjusted ORs and high-quality studies (OR, 0.66; 95% CI, 0.50 - 0.86 and OR, 0.70; 95% CI, 0.58 - 0.84, respectively). Of note, an inverse relationship was noted that metformin therapy may result in a significant decrease in the advanced adenoma risk (OR, 0.52; 95% CI, 0.38 - 0.72). Low heterogeneity was observed, however, the results remained robust in multiple sensitivity analyses.
  
  
  CONCLUSIONS
  This meta-analysis indicates that metformin therapy is correlated with a significant decrease in the risk of CRA and advanced adenoma in T2D patients. Further confirmatory studies are warranted.
authors.affiliation: Division of Gastroenterology and Hepatology, Key Laboratory Gastroenterology and Hepatology, Ministry of Health, State Key Laboratory for Oncogenes and Related Genes, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai 200001, China.
authors.forename: Yi-Chao
authors.initials: YC
authors.lastname: Hou
authors.affiliation: Division of Gastroenterology and Hepatology, Key Laboratory Gastroenterology and Hepatology, Ministry of Health, State Key Laboratory for Oncogenes and Related Genes, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai 200001, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hu
authors.affiliation: Division of Gastroenterology and Hepatology, Key Laboratory Gastroenterology and Hepatology, Ministry of Health, State Key Laboratory for Oncogenes and Related Genes, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai 200001, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Huang
authors.affiliation: Division of Gastroenterology and Hepatology, Key Laboratory Gastroenterology and Hepatology, Ministry of Health, State Key Laboratory for Oncogenes and Related Genes, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai 200001, China.
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Fang
authors.affiliation: Division of Gastroenterology and Hepatology, Key Laboratory Gastroenterology and Hepatology, Ministry of Health, State Key Laboratory for Oncogenes and Related Genes, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai 200001, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Xiong
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D000368:Aged; D016009:Chi-Square Distribution; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged; D016017:Odds Ratio; D011379:Prognosis; D065840:Protective Factors; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin
keywords: advanced adenoma; colorectal adenoma; diabetes; meta-analysis; metformin