While uncircumcised men don't seem to be at higher risk of acquiring human papillomavirus (HPV), it takes them longer to clear the virus from their bodies, new research shows. Because HPV causes genital warts and certain cancers, the finding, say researchers, could help explain why uncircumcised men have a higher risk of such penile cancers.
It could also play a role in how likely their partners are to develop infections.
"Our study demonstrates that the apparent protective influence of circumcision against genital HPV infection may not involve a reduction in new infections but rather the enhanced ability to resolve existing HPV infections," Dr. Brenda Y. Hernandez of the Cancer Research Center of Hawaii in Honolulu and her colleagues write.
But why this might be, and whether circumcision would be a good way to help prevent the spread of HPV-related disease, remains unclear, according to the researchers.
Some HPV strains cause cervical cancer in women, and are the targets of the vaccines Cervarix and Gardasil. Some strains may also be associated with penile cancer in men.
There's evidence that circumcision lowers a man's likelihood of developing cancer of the penis and contracting HPV infection, as well as HIV infection, in some populations. Because partners of uncircumcised men face a higher risk of cervical cancer, it's possible that circumcision could affect the spread of the virus as well, Hernandez and her team note.
The researchers had previously found that circumcised men were less likely than their uncircumcised peers to be infected with HPV at a given point in time. To determine if circumcision might influence a man's risk of acquiring HPV infection, as well as how readily he could clear the virus from his body, the researchers followed 357 men for an average of about 14 months. Every two months, the men, 290 of whom were circumcised, underwent HPV testing.
During the study, the researchers identified 536 different HPV infections, with no difference in risk between the circumcised and uncircumcised men. However, the researchers did find that HPV infections of the head, or glans, of the penis lasted 154 days, on average, in the uncircumcised men, compared to 91 days in the men who were circumcised. The increased duration was seen for both cancer-associated and non-cancer-associated HPV strains.
Cancer of the penis most commonly develops in the glans, Hernandez and her team point out, and the fact that infection with cancer-related strains lasted longer in uncircumcised men "has clinical significance."
It's possible, they add, "that transmission of HPV to sex partners is more efficient among uncircumcised men because of the greater duration of their infection." However, they add, "whether circumcision is an effective means of facilitating HPV clearance has yet to be demonstrated."