SAN FRANCISCO—Among obese white men, those with diabetes mellitus (DM) are more likely than non-diabetics to have high-grade prostate cancer discovered on prostate biopsy, according to researchers.

Investigators at Duke University Medical Center in Durham, N.C., studied 1,031 men undergoing their first prostate biopsy at the Durham VA Medical Center. Diabetes was present in 290 patients (28%) at the time of biopsy. A history of DM was associated with black race and higher BMI.

DM was not associated with prostate cancer risk overall, but in multivariate analysis, diabetes was significantly associated with a twofold increased risk of high-grade disease (Gleason score above 7). The association was stronger among obese men, in whom diabetes conferred a 3.76 times increased risk of high-grade disease. The researchers, led by Stephen J. Freedland, MD, observed no significantly increased risk among non-obese men.

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After further stratification by race, DM was associated with high-grade disease only in obese white men, in whom diabetes increased the risk nearly fivefold. DM was not associated with the risk of low-grade disease in all men.

Researchers reported their findings at the American Urological Association annual meeting.

In a previous study published in Cancer Epidemiology, Biomarkers & Prevention (2010;19:9-17), Dr. Freedland and colleagues demonstrated that DM at the time of radical prostatectomy was associated with worse outcomes for obese white men, including a 2.5-fold increased risk of biochemical recurrence. Black men and non-obese white men had better outcomes.

“These two relatively independent findings both suggest race and obesity may modify the association between DM and aggressive prostate cancer,” said the study’s first author, Daniel M. Moreira, MD, a urological oncology fellow at Duke.

Dr. Freedland observed that “it is likely that a combination of biologic and behavioral factors may be responsible for our observed associations between DM and prostate cancer.”