The human papillomavirus (HPV), which is often sexually transmitted, is responsible for a rapidly growing type of oral cancer. And now new research may help explain why men get the cancer more than women do.
In the first study to examine the prevalence of oral HPV infection nationwide, rates of infection among men were about three times higher than among women.
Men are also three times more likely than women to develop head and neck cancers caused by HPV, says oncologist and researcher Maura L. Gillison, MD, PhD, of Ohio State University.
About 7% of U.S. Adults Have Oral HPV Infection
Gillison and colleagues estimate that about 7% of adults in the U.S. are infected with oral HPV and that the most prevalent type of the virus associated with oral infection is HPV-16 -- the same sexually transmitted viral strain that causes a significant percentage of cervical cancers.
The study was published online today in the Journal of the American Medical Association to coincide with its presentation at the Multidisciplinary Head and Neck Cancer Symposium in Phoenix, Ariz.
"By 2020, there will be more HPV-positive oral cancers among men than cervical cancers among women in the U.S., and right now we don't even have a way to screen for them," Gillison says.
Less than a decade ago, tobacco and alcohol were believed to cause most oropharyngeal cancers -- a type of oral cancer that mostly affects the base of the tongue and the back of the mouth, including the tonsils -- that mostly strike older men who are heavy smokers and drinkers.
HPV infection is now known to cause a subset of the cancer that is increasingly diagnosed in the United States. The cancer is not closely related to tobacco and alcohol use and is most common among younger, white men.
Oral HPV Often Sexually Transmitted
In an effort to better understand oral HPV infection and how it impacts head and neck cancer risk, Gillison and colleagues analyzed mouth-rinse samples from a group of people between the ages of 14 to 69 who participated in a 2009-2010 national health survey.
Among the major findings:
- 10.1% of the men and 3.6% of the women showed evidence of oral HPV infection.
- Oral infection with HPV-16 was about three times more common in men than in women.
- Oral HPV infection was less common in people with no history of sexual contact.
- People who had the most sexual partners tended to have the highest risk for oral HPV infection.
"Our data provide evidence that oral HPV infection is predominantly sexually transmitted," the researchers write.
Vaccinating Boys Against HPV
Gillison says the study is an essential first step in developing an effective HPV-related oropharyngeal cancer prevention strategy.
Last October, a federal advisory panel recommended that the HPV vaccine be given to boys beginning at age 11 or 12, but only a very small percentage of boys in the U.S. have gotten the three-dose vaccine series.
In an editorial published with the study, Hans P. Schlecht, MD, writes that the available vaccines have been shown to be highly effective for preventing HPV infection at other sites.
He tells WebMD that while the research proving that vaccination prevents oral HPV infection in humans is lacking, it is reasonable to assume that it does. Both HPV vaccines on the market target HPV-16, the most prevalent type of oral HPV.
Schlecht is an assistant professor of medicine in the Division of Infectious Diseases and HIV Medicine at Drexel University College of Medicine in Philadelphia.