Background: The worldwide incidence of diabetes mellitus is rapidly increasing. There is recent interest in the influence of glucose metabolism on oncogenesis. We investigated the role of diabetes mellitus and the metabolic syndrome (MS) on prostate cancer development.
Methods: This study consisted of 11 541 men with coronary heart disease screened to participate in a secondary cardiac prevention trial. MS was defined according to modified NCEP/ATP III criteria. Multivariable regression analysis accounting for competing risks was performed using a modified Cox proportional hazard model in order to assess the association between diabetes, the MS and the subsequent development of prostate cancer.
Results: At baseline, subjects were classified into one of the four groups: (1) 6119 (53%) with neither diabetic mellitus nor MS, (2) 3376 (29%) with the MS but without diabetes, (3) 560 (5%) with diabetes mellitus but without MS and (4) 1486 (13%) with both conditions. Median follow-up was 12.7 years (range 0-15.7 years). During follow-up, 459 new cases of prostate cancer were recorded. The age-adjusted hazard ratio (HR) for prostate cancer was reduced in diabetic patients compared with those without diabetes, 0.54 and 95% confidence interval of 0.40-0.73. No significant association was noted between the presence of MS and prostate cancer development. On multivariate analysis, diabetes mellitus continued to protect against the development of prostate cancer, this was more pronounced in the absence of MS (HR=0.43, P=0.01 for diabetes in the absence of MS; HR=0.64, P=0.08 in the presence of MS).
Conclusions: The results of this study indicate an inverse association between type 2 diabetes mellitus and prostate cancer risk.