Researchers suspect the connection may be the lower rate among circumcised men of sexually transmitted diseases (STD), which raise prostate cancer risk, but they caution that more study is needed to confirm that theory.
"It’s still premature to say go ahead with circumcision to prevent prostate cancer," said lead author Marie-Elise Parent. "But, we think it could be helpful."
Based on interviews with more than 3,000 men, her team found that those circumcised as infants were 14% less likely than uncircumcised men to develop prostate cancer. The men who had been circumcised as adults were 45% less likely to develop the cancer than uncircumcised men.
Researchers have long known that Muslim and Jewish men have lower rates of prostate cancer than men in the West, suggesting that circumcision may play a role in cancer risk, the study team writes in the British urology journal BJU International.
To investigate the connection, Parent, a cancer epidemiologist at the University of Quebec’s INRS-Institut Armand-Frappier in Montreal, and her colleagues recruited 3,208 men in the Montreal area.
The participants were all between 40 and 75 years old when they were recruited and 1,590 of them had been diagnosed with prostate cancer. The other 1,618 men did not have prostate cancer but were otherwise similar in health and age.
Between 2006 and 2011, all the men were interviewed at home, with in-depth questions about their health and lifestyle, medical history, family history of cancer and work history.
Overall, 40% of white men and 30% of black men interviewed were circumcised.
For the entire group, researchers found an 11% lower risk of having prostate cancer among circumcised men, but noted that it was not statistically significant, meaning it could have been due to chance.
The team did find a significant difference among circumcised black men, who were 60% less likely than uncircumcised men to have prostate cancer.
"Black men have the highest rate (of prostate cancer) on the planet and we don’t know why,” Parent told Reuters Health. “It’s really puzzling trying to figure out why this cancer is so common in men that live in industrialized countries, when we understand so little about what’s going on with it and have no way of preventing it."
Too early in the game to make recommendation
The National Cancer Institute estimates that in the US, almost three million men are living with prostate cancer. It is the second leading cause of cancer deaths among men.
About 79% of US men born in the 1970s and 1980s were circumcised as babies, according to Dr. Aaron Tobian of Johns Hopkins University in Baltimore, Maryland. But the circumcision rate has been declining, he told Reuters Health.
Among males born in the US in 1999, 62.5% were circumcised, and by 2010, the rate among newborns was below 55%, Tobian said.
Medicaid does not typically cover the procedure, which could lead to exaggerated socio-economic differences in STD-related health, Tobian added. “Insurers are also trending toward decreasing coverage for circumcision,” he said.
Dr. Christopher Cooper, a professor and urologist at the University of Iowa told Reuters Health that the Canadian study does not justify promoting circumcision as prostate cancer prevention.
The number of black men studied was too small for any conclusions to be drawn, he notes. Only 103 of the participants with prostate cancer were black men, and only 75 of the healthy men in the comparison group were black.
“The STD mechanism is possible but quite a stretch,” Cooper said. He also pointed out that there were certain factors the researchers could not control in the study, such as how honest participants were about having STDs or, among the men circumcised as adults, the reason for their circumcision.
Parent told Reuters Health that even though the study was small, and she and her colleagues saw only a slightly reduced risk later in life among men who were circumcised as babies, the work is one more thing to consider when studying prostate cancer.
“We are too early in the game to make it a public recommendation. It could be that in the future it will be confirmed that it’s a good thing and may have an added protection from other diseases,” she added.