Diabetes, prostate cancer link: Surprising, or not?

Dr. Albertsen, a member of the Urology Times Editorial Council, is professor of surgery and chief of urology at the University of Connecticut Health Center, Farmington.

At the recent European Association of Urology annual congress, researchers from Italy and Canada presented a poster exploring the association between diabetes and high-grade prostate cancer (see page 1). They identified over 100,000 men diagnosed between 1992 and 2005 from the SEER registry and found that 14% of these men were diabetic. A surprising number of these men harbored high-grade or locally advanced prostate cancer. After controlling for various covariates, the authors concluded that diabetic men were 5% more likely to harbor poorly differentiated disease.

While intriguing, these findings should only be viewed as hypothesis generating. Retrospective data analysis is prone to selection biases that can seriously confound findings. The population of men with high-grade tumors had a greater proportion of African-Americans, a group known to harbor a much higher incidence of clinically significant prostate cancer when compared to Caucasians.

Furthermore, the population of men with high-grade and advanced tumors had a greater proportion of men from lower socioeconomic classes. Men living in poverty are much less likely to have appropriate routine health care and therefore are more likely to present with advanced prostate cancer. These men are also known to have a higher incidence of diabetes. A modest correlation between diabetes and high-grade prostate cancer is therefore not as surprising as it may seem. To conclude that diabetes somehow places men at risk for high-grade or advanced cancer requires considerably more evidence.

For now, clinicians should regard diabetic men as they do other men presenting for routine urologic care. Evidence from the European Randomized Study of Screening for Prostate Cancer suggests that men aged 55 to 69 years may benefit from PSA testing. This is true for diabetic men and non-diabetic men. Men with milder forms of diabetes appear to be at the same risk of developing prostate cancer as men without this disease.

Unfortunately, men with advanced diabetes and end-organ disease are unlikely to survive 10 to 15 years and therefore will probably not benefit from routine PSA testing. Men with abnormal findings on digital rectal exam or other indicators of prostate cancer should be tested, but the evidence is insufficient to justify preferentially screening diabetic men because they may be at a higher risk of developing clinically significant prostate cancer.UT