Circumcision was linked to a 60% decrease in prostate cancer risk in black men, according to a large case-control study published online May 28 in BJU International.
"Very little evidence has accrued to date on the role of circumcision in prostate cancer risk among black men, known to have the highest rates of the disease. This clearly deserves further research," said Dr. Andrea Spence of the University of Quebec.
In the study, black men were less likely than were white men to be circumcised (30% versus 40% respectively), and were more likely to have had sexually transmitted infections (STIs) when they were uncircumcised (28%) than when they were circumcised (10%), noted Dr. Spence and her associates. "Such an STI pattern by circumcision status was not seen among white men," they added. "Although STI history was adjusted for within models, residual confounding may potentially explain the protective effect of circumcision in black men" (BJU Inter. 2014 May 28 [doi: 10.1111/bju.12741]).
Circumcision appeared to protect other study groups against prostate cancer, but associations did not reach statistical significance except in men circumcised at age 36 years or older, the researchers said. This was the first known report of such an association, and they did not know the reason, they added.
The population-based case-control study comprised 1,590 pathologically confirmed prostate cancer cases diagnosed in a Montreal hospital between 2005 and 2009, and 1,690 age-matched controls. Researchers interviewed cases and controls to measure demographic, lifestyle, and environmental factors. They used unconditional logistic regression to look at relationships between circumcision, age at circumcision, and prostate cancer risk while adjusting for age, ancestry, education, family history of prostate cancer, history of screening for prostate cancer, and history of STIs.
Circumcision was linked to an 11% decrease in prostate cancer risk in the overall study population, but the effect did not reach significance (odds ratio, 0.89; 95% confidence interval, 0.76-1.04) except in black men (OR, 0.40; 95% CI, 0.19-0.86; P = .02) and men circumcised at age 36 years and older (OR, 0.55; 95% CI, 0.30-0.98), reported Dr. Spence and her associates. In all, 2.6% of controls were circumcised at this older age, compared with 1.3% of cases, they added. The association in this subgroup remained significant even after the researchers controlled for factors linked to lower prostate cancer rates, such as type 2 diabetes, they said.
Circumcision status was self-reported and generally not verified by chart reviews.
The Canadian Cancer Society, Cancer Research Society, Fonds de la recherche du Québec – Santé (FRQS), FRQS-RRSE, the Minisétre du Développement Économique de l’Innovation et de l’Exportation du Québec, and the Canadian Institutes for Health Research funded the study. The authors disclosed no conflicts of interest.