title: The use of metformin and colorectal cancer incidence in patients with type II diabetes mellitus.
abstract: BACKGROUND
  Experimental studies have suggested that metformin may decrease the incidence of colorectal cancer in patients with type II diabetes. However, previous observational studies have reported contradictory results, which are likely due to important methodologic limitations. Thus, the objective of this study was to assess whether the use of metformin is associated with the incidence of colorectal cancer in patients with type II diabetes.
  
  
  METHODS
  A cohort study of patients newly treated with non-insulin antidiabetic agents was assembled using the United Kingdom Clinical Practice Research Datalink. A nested case-control analysis was conducted, where all incident cases of colorectal cancer occurring during follow-up were identified and randomly matched with up to 10 controls. Conditional logistic regression was used to estimate adjusted rate ratios (RR) of colorectal cancer associated with ever use, and cumulative duration of use of metformin. All models accounted for latency and were adjusted for relevant potential confounding factors.
  
  
  RESULTS
  Overall, ever use of metformin was not associated with the incidence of colorectal cancer [RR: 0.93; 95% confidence interval (CI), 0.73-1.18]. Similarly, no dose-response relationship was observed in terms of cumulative duration of use.
  
  
  CONCLUSIONS
  The use of metformin was not associated with the incidence of colorectal cancer in patients with type II diabetes.
  
  
  CONCLUSIONS
  The results of this study do not support the launch of metformin randomized controlled trials for the chemoprevention of colorectal cancer.
authors: Authors' Affiliations: Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital; and Departments of Epidemiology, Biostatistics, and Occupational Health and Oncology, McGill University, Montreal, Quebec, Canada.
authors: Brielan
authors: B
authors: Smiechowski
authors: Laurent
authors: L
authors: Azoulay
authors: Hui
authors: H
authors: Yin
authors: Michael N
authors: MN
authors: Pollak
authors: Samy
authors: S
authors: Suissa
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage*; D008297:Male; D008687:Metformin / Q000008:administration & dosage*; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin