HPV (human papillomavirus) vaccines protect against the sexually transmitted strains of HPV that cause cervical cancer. The same HPV strains -- spread by kissing and by oral sex -- cause oropharyngeal (OP) cancer, the form of head and neck cancer that affects the back and sides of the throat, the base of the tongue, and the tonsils.
There's strong evidence that HPV vaccines prevent cervical cancer. There's no direct proof that these vaccines prevent throat cancer, but the rapid rise in cases among young people has some experts wanting to vaccinate first and get proof later.
"We don't need to wait until all these molecular events are understood," Dong Moon Shin, MD, of Emory University's Winship Cancer Center, tells WebMD. "The time is now. For the HPV vaccine, cost is the only issue as side effects are minimal. Routine HPV vaccination has to be implemented very soon, for both boys and girls."
In the U.S., that recommendation is made by the Advisory Committee on Immunization Practices (ACIP). The ACIP now recommends routine HPV vaccination only for girls and young women in order to prevent cervical cancer. It permits vaccination of boys who want protection against HPV-caused genital warts.
For two years, the ACIP has been mulling whether to recommend the HPV vaccine for boys. This would help prevent cervical cancer in unvaccinated women. It also would prevent HPV-related anal cancer and genital warts in both men and women, as well as HPV-related cancer of the penis.
But HPV causes anal cancer and penile cancer far less often than it causes cervical cancer, and if enough girls were to get the HPV vaccine -- about 50% -- it wouldn't be cost-effective to vaccinate boys.
Throat cancer is rapidly changing this scenario.
Throat Cancer Tipping Scales Toward HPV Vaccination of Boys
At yesterday's meeting, the ACIP heard a disturbing report from Aimee Kreimer, PhD, an expert in head and neck cancer at the National Cancer Institute.
"At some point ... it is projected that there will be the same incidence of OP cancer in men as cervical cancer in women," Kreimer said. "If current trends continue, OP cancer in men will pass cervical cancer in 2025."
And HPV is to blame. Only a few decades ago, the major risk factors for throat cancer were smoking and alcohol. Not any more. In the five-year period of 1984-1989, only 16% of OP cancers were linked to HPV. By 2000-2004, HPV was behind 75% of OP cancers.
What are the risk factors? Not all are known, but HPV-related throat cancer risk goes up with increased oral sex and kissing, Kreimer said. Current tobacco use and HIV infection also are risks.
Fortunately, oral HPV infection appears to be much less common than genital HPV infection. Among healthy individuals infected with HPV, fewer than one in 20 has detectable HPV in the oral cavity.
But there are disturbing trends. Husbands of women with cervical cancer have a threefold higher risk of tonsil cancer. And people who have anal cancer have a fourfold to sixfold higher risk of tonsil cancer.
These findings are tipping the ACIP in favor of recommending routine HPV vaccination for boys.
"Most members of the [ACIP] HPV working group favor the strategy of routine vaccination of all males at the age at which they get the most benefit," Eileen Dunne, MD, MPH, a CDC researcher assisting the working group, said in a presentation to the full ACIP.
But the ACIP did not vote on the issue at the June meeting. Some members of the panel expressed frustration with the process.
"HPV cancers in males account for 7,000 cases a year," said ACIP member Mark H. Sawyer, MD, professor of pediatrics at the University of California, San Diego. "That is not a trivial number, and we are sitting around here wondering whether to immunize them. But it is not a trivial question."
The National Cancer Institute estimated that in 2010, there were 12,660 cases of OP cancer -- and 2,410 deaths. About half of those cases would have been male; at least three-fourths would have been caused by HPV.
The full ACIP likely will vote on the issue at its October meeting.