Antidiabetic medication and prostate cancer risk: a population-based case-control study.

Decreased risk of prostate cancer in diabetic men has been reported. The authors evaluated the association between antidiabetic medication use and prostate cancer at the population level. All incident prostate cancer cases in Finland during 1995-2002 were identified from the Finnish Cancer Registry. Matched controls were provided by the Population Register Center (24,723 case-control pairs). Information on medication use was obtained from a comprehensive prescription database. Multivariable-adjusted odds ratios were computed by using conditional logistic regression. The authors found that prostate cancer risk was decreased for antidiabetic medication users (odds ratio = 0.87, 95% confidence interval: 0.82, 0.92). The decrease was observed for most drug groups. The odds ratio decreased in a dose-dependent fashion by quantity of use. Duration of antidiabetic treatment was inversely associated with overall prostate cancer risk and risk of advanced cancer. Similar risk reduction for users of different antidiabetic drugs suggests that diabetes, instead of the medication itself, is behind the association. This finding is unlikely to be secondary because of differential uptake of the prostate-specific antigen test or different prostate-specific antigen levels between medication users and nonusers; prevalence of testing in Finland is low. Dose and time dependency of the relation probably indicates that duration of diabetes is negatively associated with risk.