title: Does metformin affect the incidence of colonic polyps and adenomas in patients with type 2 diabetes mellitus?
abstract: OBJECTIVE
  Colorectal cancer (CRC) develops from colonic adenomas. Type 2 diabetes mellitus (DM) is associated with a higher risk of CRC and metformin decreases CRC risk. However, it is not certain if metformin affects the development of colorectal polyps and adenomas. This study aimed to elucidate if metforminaffects the incidence of colonic polyps and adenomas in patients with type 2 DM.
  
  
  METHODS
  Of 12,186 patients with type 2 DM, 3,775 underwent colonoscopy between May 2001 and March 2013. This study enrolled 3,105 of these patients, and divided them in two groups: 912 patients with metformin use and 2,193 patients without metformin use. Patient clinical characteristics, polyp and adenoma detection rate in the two groups were analyzed retrospectively.
  
  
  RESULTS
  The Colorectal polyp detection rate was lower in the metformin group than in the non-meformin group (39.4% vs. 62.4%, P<0.01). Colorectal adenoma detection rate was significantly lower in the metformin group than in the non-metformin group (15.2% vs. 20.5%, P<0.01). Fewer advanced adenomas were detected in the metformin group than in the non-metformin group (12.2% vs. 22%, P<0.01). Multivariate analysis identified age, sex, Body mass index and metformin use as factors associated with polyp incidence, whereas only metforminwas independently associated with decreased adenoma incidence (Odd ratio=0.738, 95% CI=0.554-0.983, P=0.03).
  
  
  CONCLUSIONS
  In patients with type 2 DM, metformin reduced the incidence of adenomas that may transform into CRC. Therefore, metformin may be useful for the prevention of CRC in patients with type 2 DM.
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Youn Hee
authors.initials: YH
authors.lastname: Cho
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Bong Min
authors.initials: BM
authors.lastname: Ko
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Shin Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Yu Sik
authors.initials: YS
authors.lastname: Myung
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Jong Hyo
authors.initials: JH
authors.lastname: Choi
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Jae Pil
authors.initials: JP
authors.lastname: Han
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Hong
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Seoul, Korea.
authors.forename: Seong Ran
authors.initials: SR
authors.lastname: Jeon
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Seoul, Korea.
authors.forename: Hyun Gun
authors.initials: HG
authors.lastname: Kim
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Seoul, Korea.
authors.forename: Jin Oh
authors.initials: JO
authors.lastname: Kim
authors.affiliation: Digestive Disease Center and Research Institute, Department of Internal Medicine, Soon Chun Hyang University College of Medicine, Bucheon, Korea.
authors.forename: Moon Sung
authors.initials: MS
authors.lastname: Lee
keywords: Adenoma detection rate; Colon adenoma; Diabetes mellitus, type 2; Metformin; Polyp detection rate