A Meta-Analysis Of Diabetes Mellitus And The Risk Of Prostate Cancer

UroToday.com- In 2004 a meta-analysis reported that patients with diabetes mellitus (DM) had a statistically significant decrease in risk (9%) of developing prostate cancer (CaP). This has now been validated in a larger meta-analysis reported by Drs. Kasper and Giovannunucci from Harvard Medical School. Their report appears in the November 2006 issue of Cancer Epidemiology Biomarkers and Prevention.

The goal of the new meta-analysis was to increase the number of articles included in the analysis from 14 to 19 and thereby the number of cases from 9,000 to >20,000 for enhanced statistical analysis. The authors also sought to determine if differences existed in patients in the pre-PSA compared to PSA era. The selection of published studies identified 325 articles of which 19 were chosen for extraction and analysis. While most publications did not specify whether patients had type I or type II DM, the age of participants suggested that most had type II DM. A variety of subset analyses were performed to address particular questions.

To determine the amount of heterogeneity that existed between the 19 studies a Cochran's Q test was performed. Then using a random-effects model, the authors found that DM was associated with a lower risk for CaP (RR, 0.84). Both cohort and case-control studies demonstrated heterogeneity. When analyzed by publication year, less heterogeneity existed as a group for the studies published prior to 2002 or after 2002 compared to all the studies combined.

To determine any difference in risk in the pre- and post-PSA eras, another subgroup analysis was done. The RR for pre-PSA was 0.94 and the RR for PSA era was 0.73. Separating studies that corrected for BMI from those that did not correct for BMI showed RRs of 0.82 and 0.87, respectively. Overall, the study showed that diabetic men have a statistically significant 16% decreased risk of developing CAP. The authors cite several possible explanations. DM and CaP may share additional factors that affect the risk of both diseases independently. This could include decreased insulin and IGF-I levels, or decreased testosterone levels.

This larger, robust meta-analysis strongly validates that men with DM are at decreased risk for development of CaP.

Jocelyn S. Kasper and Edward Giovannucci
Cancer Epidemiol Biomarkers Prev 2006 15: 2056-2062.

Reviewed by UroToday.com Contributing Editor Christopher P. Evans, M.D. UroToday - the only urology website with original content written by global urology key opinion leaders actively engaged in clinical practice.

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