The HPV Cancer Connection: Take 2
HPV can be spread from skin-to-skin contact of areas not covered by a condom, explains Lowy. And though there isn’t any concrete evidence of how oral HPV infections are contracted, Maura L. Gillison, a head and neck medical oncologist at the Ohio State University in Columbus, who led the recent JAMA study, notes that some preliminary research has suggested that the virus may potentially be spread by mouth-to-mouth or hand-to-mouth contact.
Vaccination—Not Just for Girls?
The prevalence of HPV was part of the basis for a 2007 recommendation by the CDC’s Advisory Committee on Immunization Practices that all girls get vaccinated at age 11 or 12; the vaccine is most effective if given before a person becomes sexually active.
Despite the recommendation, Einstein says, some parents remain concerned that the vaccine might cause dangerous side effects. But, he says, ongoing research investigating the vaccine’s safety has found only minimal side effects, like temporary swelling or pain at the injection site, which are similar to side effects associated with other vaccinations. (See “HPV Prevention: What vaccines are available?” for more information about the Gardasil and Cervarix vaccines.
“Some people may have a low-grade fever, and some adolescent girls have fainted within a few minutes of getting the vaccine,” adds Lowy. “But these are recognized side effects of most vaccines. Claims of other side effects have not been substantiated.”
Now the vaccine isn’t being endorsed only for girls. In October 2011, the CDC began to recommend that 11- and 12-year-old boys be vaccinated, in addition to girls. The Gardasil vaccine is approved to protect boys from genital warts and anal cancer, and vaccinating boys means that fewer of them will spread the virus to girls.
Now that HPV has been shown to cause many oropharyngeal cancers, there will be interest in studying whether the vaccine can prevent oral HPV infection.
Vaccinating one segment of the population for the benefit of another isn’t new. “The rubella vaccine is given to boys and girls, but the purpose of rubella vaccination is to prevent fetal abnormalities in pregnant women,” explains Lowy. “So boys receive the vaccine for altruistic reasons. There is precedent for taking vaccines for the purpose of helping other people.”
The vaccine may have additional benefits. Beyond protecting girls and boys against genital warts and cervical or anal cancers, Lowy says, it’s theoretically possible that HPV vaccination imparts protection against other HPV-linked cancers—though there is currently no data to support such a claim. In particular, effectiveness of an HPV vaccine against oropharyngeal cancer would be hard to demonstrate, says Lowy, so it’s unlikely any vaccine will be approved for that use soon.
Cervical and anal cancers are preceded by precancerous lesions that are easy to identify and remove before they become cancer, he explains. When researchers conducted trials to prove the HPV vaccine prevented cervical and anal cancers, they used those precancerous lesions as indicators of the vaccine’s effectiveness. The vast majority of people who were given the vaccine did not develop such lesions. But precancerous lesions can’t be used as an indicator of effectiveness in oropharyngeal cancers, so researchers would need to conduct much longer trials and wait for trial participants to develop tumors, to demonstrate whether the vaccine offers any protection against them.
“The vaccine isn’t given in the genital tract,” Lowy points out. “It is given systemically into the blood stream, so there is every reason to assume that the vaccine would work for other cancers. There’s just no data.”
When the HPV vaccines were first developed, there wasn’t as much evidence linking HPV to oropharyngeal cancer, adds Gillison. But she thinks that now that HPV has been shown to cause many of these cancers, there will be interest in studying whether the vaccine can prevent oral HPV infection. However, she cautions, further study is needed before the vaccine can be recommended or approved as a way to prevent any HPV-related oropharyngeal cancers.
“I would recommend the vaccine for boys based on the existing data for prevention of anal cancer and genital warts,” says Gillison. “I don’t think, as an evidence-based scientist, that I can say, ‘Vaccinate your sons to prevent oral cancer.’ I’d love someday to be able to say that. But sometimes we’re surprised. You can never be certain: Perhaps there’s something about the oral cavity that would make the vaccine not work there.”
Whether or not the vaccines prove to be effective against HPV in other parts of the body, existing evidence shows the vaccine is already something parents should consider—and discuss with their children’s doctors.
Alanna Kennedy-Gorman is Cancer Today’s assistant editor. She lives in Collingswood, N.J.