Background: Diabetes is associated with lower prostate cancer risk. The association of diabetes with prostate cancer outcomes is less clear. We examined the association between diabetes and outcomes after radical prostatectomy and tested whether associations varied by race and/or obesity. Materials and Methods: This study is a retrospective analysis of 1,262 men treated with radical prostatectomy between 1988 and 2008 within the Shared Equal-Access Regional Cancer Hospital database. We examined the multivariate association between diabetes at surgery and adverse pathology, biochemical recurrence (BCR), and prostate-specific antigen doubling time at recurrence using logistic, proportional hazards, and linear regression, respectively. Data were examined as a whole and stratified by race and obesity. Results: Diabetes was more prevalent among black (22% versus 15%, P < 0.001) and more obese men (P < 0.001). Diabetes was associated with higher tumor grade (odds ratio, 1.73; P = 0.002), seminal vesicle invasion (odds ratio, 1.73; P = 0.04), but not BCR (P = 0.67) or PSADT at recurrence (P = 0.12). In the secondary analysis, among white obese men, diabetes was associated with 2.5-fold increased BCR risk (P = 0.002) and a trend toward shorter PSADT, whereas among all other men (nonobese white men and black men), diabetes was associated with 23% lower recurrence risk (P = 0.09) and longer PSADT (P = 0.04). Conclusion: In a radical prostatectomy cohort, diabetes was not associated with BCR. In the secondary analysis, diabetes was associated with more aggressive disease in obese white men and less aggressive disease for all other subsets. If externally validated, these findings suggest that among men with prostate cancer, the association between diabetes and prostate cancer aggressiveness may vary by race and obesity.
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