Association between diabetes, prostate cancer aggressiveness varied by race, obesity

White men with diabetes and prostate cancer had significantly worse outcomes following radical prostatectomy, according to the results of a recently published study. In addition, white men with diabetes who were also obese, had an increased risk for aggressive prostate cancer compared to non-obese counterparts.

“There is a lot of interest in the role of race, obesity and insulin in prostate cancer, particularly prostate cancer aggressiveness,” Stephen J. Freedland, MD, of the department of surgery and urology at Duke University School of Medicine, told HemOnc Today. “This article highlights first that these interactions may be complex; however, more specifically, it points us in certain directions.”

The retrospective analysis included 1,262 men (47% black; 29% obese) with prostate cancer treated with radical prostatectomy. All were included in the Shared Equal-Access Regional Cancer Hospital (SEARCH) database between 1988 to 2008.

Researchers utilized logistic, proportional hazards and linear regression models to assess the multivariate association between diabetes at prostatectomy and adverse pathology, biochemical recurrence and PSA doubling time at recurrence. Data were stratified by race and obesity.

Compared with white men, diabetes was significantly more prevalent among black men (15% vs. 22%; P=.003). However, diabetes was associated with more aggressive prostate cancer in white men compared with black men (P=.003).

Men with diabetes had a greater than 70% increased risk for high-grade prostate cancer (P=.002) and seminal vesicle invasion (P=.04), after researchers adjusted for multiple preoperative clinical features. In addition, compared with men without diabetes, men with diabetes had significantly lower PSA levels (P=.01), higher BMI (P<.001), were more likely to be recently treated (P<.001) and had higher radical prostatectomy tumor grade (P<.001).

Thirty-two percent of men developed a biochemical recurrence (BCR); however, researchers reported no association between diabetes and BCR (P=.33), even after adjusting for multiple preoperative characteristics (P=.67).

Although not significant, when researchers further stratified by race, diabetes was associated with a trend toward increased BCR among white men (HR=1.28; P=.28) and a decreased risk among black men (HR=0.79; P=.26).

Further, researchers found a 2.5-fold increased risk for BCR associated with diabetes among obese white men (P=.002) when compared with non-obese white men with diabetes, who had a 31% reduced risk for BCR (P=.26). This interaction was significant for predicting BCR among white men only (P=.006).

“The good news is that on a whole, diabetes did not make a worse cancer — in fact, the link between diabetes and poor outcome was only seen in obese white men,” Freedland said. “Thus, for the majority of normal-weight white and all black men, obesity actually was associated with a less aggressive cancer.”

“As such, unlike obesity, which does make a worse cancer, diabetes in general is not making the cancer worse and, thus, physicians can focus on treating the patient appropriately and not worry that just because the patient is diabetic their cancer will behave more aggressively,” he said. – by Jennifer Southall

Jayachandran J. Cancer Epidemiol Biomarkers Prev. 2010;19: 9–17.