A new study released Monday has found that men who are circumcised before their first sexual encounter have a 15 percent lower incidence of prostate cancer than men who are uncircumcised or were circumcised after they first had sex.
Researchers say that because circumcised men are slightly less likely to contract herpes and human papillomavirus (HPV) than uncircumcised men, which previous studies have linked to a higher incidence of prostate cancer, circumcision might offer a level of protection against the disease.
Janet Stanford, of the Fred Hutchinson Cancer Research Center and one of the authors of the report, which was published in the journal Cancer, says the study was a "natural extension" of ones that linked STDs to prostate cancer rates.
"It's not a new hypothesis, this is just another piece of the puzzle" to determining what causes prostate cancer, she says. "It's a procedure we have good reason to think would reduce exposure to potential sexually transmitted agents and thereby may prevent inflammation in the prostate, which is associated with a reduced risk of developing prostate cancer."
Stanford says previous studies have shown "the potential that there was something related to sexual encounters" associated with prostate cancer. By that logic, wouldn't condom use, abstinence, or practicing safe sex provide the same or better benefits than circumcision?
"We didn't address that question," Stanford says. "That's a totally different question in terms of types of exposure to sexually transmitted agents … hopefully this will raise a lot of interest in expanding the whole issue."
Tenuous links associating behavior with prostate cancer rates have a long history, says Ron Gray, a researcher at Johns Hopkins University's Bloomberg School of Public Health who focuses on reproductive health and epidemiology.
"There's a number of reports that are all observational studies reporting things like lifetime sex partners or a history of sexually transmitted diseases lead to a somewhat increased risk of prostate cancer," Gray, who is not familiar with the Fred Hutchinson Center report, says. "The literature is very confused. Past studies have linked vasectomies, sexual histories, STDs--none of which are very convincing in my mind."
The problem with prostate cancer studies, he says, is that the disease is so prevalent--up to 30 percent of 50-year-old men may have "what physiologically appears to be prostate cancer." A large number of those cases will stay confined to the prostate, causing few, if any symptoms. Trying to find an underlying cause for that type of cancer is difficult and oftentimes pointless, he says. "We have probably been over-diagnosing and over-treating cases that are detected by screens and are not destined to be tumors. Many of these men will die with, rather than die from prostate cancer," Gray says.
The key, he says, is determining what causes the more aggressive form of prostate cancer that can spread through the body and potentially kill a patient. The Fred Hutchinson Center report tracked patients with both the less aggressive and more aggressive forms of prostate cancer; circumcised men were less likely to have either form.
"No observational data can ever prove causation," Stanford says. "But we now have indirect evidence that, as a group, men who are circumcised have a lower rate of prostate cancer."