title: Metformin use and prostate cancer risk.
abstract: BACKGROUND
  Metformin may decrease prostate cancer (PCa) risk by reducing hyperinsulinemia-associated carcinogenesis or through direct effects on cancer cells.
  
  
  OBJECTIVE
  To evaluate the association between metformin use and PCa diagnosis.
  
  
  METHODS
  We used the Danish Cancer Registry and the Aarhus University Prescription Database to conduct a nested case-control study among men residing in northern Denmark from 1989 to 2011. We identified 12 226 cases of PCa and used risk-set sampling to select 10 population controls per case (n=122,260) from among men alive on the index date and born in the same year. A sensitivity analysis was conducted using subjects who had prostate-specific antigen (PSA) testing prior to 1 yr before the index date.
  
  
  METHODS
  Metformin exposure was assessed using prescriptions redeemed before the index date.
  
  
  METHODS
  Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression. The association between metformin use and PCa diagnosis was determined, controlling for diabetes severity and other potential confounders.
  
  
  CONCLUSIONS
  Metformin users were at decreased risk of PCa diagnosis compared with never-users (adjusted OR [aOR]: 0.84; 95% CI, 0.74-0.96). Diabetics on no medication (aOR: 0.98; 95% CI, 0.89-1.09) or on other oral hypoglycemics (aOR: 0.98; 95% CI, 0.86-1.10) did not have a reduced risk of PCa, while users of insulin did have a reduced risk (aOR: 0.77; 95% CI, 0.64-0.93). In the PSA-tested group, metformin use was associated with decreased risk of PCa compared with nonuse (aOR: 0.66; 95% CI, 0.51-0.86). Diabetics on no medication (aOR: 1.03; 95% CI, 0.86-1.24), diabetics on other oral hypoglycemics (aOR: 0.92; 95% CI, 0.70-1.20), and insulin users (aOR: 0.83; 95% CI, 0.56-1.24) did not have a statistically significant reduced risk of cancer.
  
  
  CONCLUSIONS
  Metformin use was associated with decreased risk of PCa diagnosis, whereas diabetics using other oral hypoglycemics had no decreased risk.
  
  
  RESULTS
  We studied the relationship between metformin (a diabetic medication) and prostate cancer in Denmark. We found that metformin reduced the risk of prostate cancer diagnosis, whereas other oral antidiabetic medications did not.
authors.affiliation: Department of Urology, Massachusetts General Hospital, Boston, MA, USA. Electronic address: preston.mark@gmail.com.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Preston
authors.affiliation: Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Riis
authors.affiliation: Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark.
authors.forename: Vera
authors.initials: V
authors.lastname: Ehrenstein
authors.affiliation: The Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Rodney H
authors.initials: RH
authors.lastname: Breau
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA; Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Julie L
authors.initials: JL
authors.lastname: Batista
authors.affiliation: Department of Urology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Aria F
authors.initials: AF
authors.lastname: Olumi
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA; Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Lorelei A
authors.initials: LA
authors.lastname: Mucci
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hans-Olov
authors.initials: HO
authors.lastname: Adami
authors.affiliation: Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark.
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003718:Denmark / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000188:drug therapy; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D015994:Incidence; D007328:Insulin / Q000627:therapeutic use; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged; D016017:Odds Ratio; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D012042:Registries; D018570:Risk Assessment
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D008687:Metformin
keywords: Chemoprevention; Danish registry; Epidemiology; Incidence; Metformin; Prostate cancer