Diabetes mellitus, race and the odds of high grade prostate cancer in men treated with radiation therapy

Purpose: Black men present more frequently with high grade prostate cancer and are more likely to have diabetes mellitus. We evaluated whether there is an independent association between diabetes mellitus and the risk of high grade prostate cancer in men diagnosed with prostate cancer and treated with radiation therapy. Materials and Methods: A polychotomous logistic regression analysis was performed to evaluate whether a diagnosis of diabetes mellitus was associated with the odds of Gleason score 7 or 810 prostate cancer in a cohort of 16,286 men, adjusting for black race, advancing age, prostate specific antigen and digital rectal examination findings. Results: Black men (adjusted OR 1.84, 95% CI 1.083.13, p = 0.024) and nonblack men (adjusted OR 1.59, 95% CI 1.331.89, p <0.001) with diabetes were more likely to have Gleason score 810 vs 6 or less prostate cancer than nondiabetic men. However, this was not true for Gleason score 7 vs 6 or less prostate cancer. Black race was significantly associated with Gleason score 7 vs 6 or less prostate cancer in men without and with diabetes (adjusted OR 1.38, 95% CI 1.171.63, p <0.001 and 1.61, 95% CI 1.172.21, p = 0.003, respectively). Black race was also associated with Gleason score 810 vs 6 or less prostate cancer in men without and with diabetes (adjusted OR 1.36, 95% CI 1.011.83, p = 0.04 and 1.58, 95% CI 0.982.53, p = 0.06, respectively). Conclusions: In a cohort of men undergoing radiotherapy for prostate cancer the diagnosis of diabetes mellitus was significantly associated with an increased risk of being diagnosed with Gleason score 810 prostate cancer independent of black race.