WASHINGTON -- The sexually transmitted virus that causes cervical cancer also sharply increases the risk of certain types of throat cancer among people infected through oral sex, according to a study being published today.
The study, involving 300 subjects with and without throat cancer, found that those infected with the human papillomavirus, or HPV, were 32 times more likely to develop one form of oral cancer than those free of the virus. Although previous research had indicated HPV caused oral cancer, the new study is the first to definitively establish the link, researchers said.
"It makes it absolutely clear that oral HPV infection is a risk factor," said Maura Gillison, an assistant professor of oncology and epidemiology at the Johns Hopkins Medical Institutions in Baltimore, who led the study published in The New England Journal of Medicine.
The findings could help explain why oral cancer rates have been increasing in recent years, particularly among younger people and those who are not smokers or heavy drinkers, long the primary risk groups, researchers said.
"There's been a kind of sea change in the last ten years in who we're seeing with these cancers," Gillison said. "It makes sense with some changes we've seen in sexual behavior."
The findings provide new evidence that oral sex is not safe sex, despite widespread misconceptions to the contrary, particularly among adolescents.
"Many adolescents, and adults too, say they engage in oral sex as a less risky type of sex," said Mark A. Schuster of the Rand Corp. and UCLA, noting that herpes, syphilis, gonorrhea, HIV, and other sexually transmitted infections also spread through oral sex. "What this article and others show is you absolutely can get serious sexually transmitted diseases through oral sex."
The findings could also provide new ammunition for those advocating wide use of a new vaccine that protects against HPV. Even though the vaccine has not been tested specifically to see if it reduces the risk of oral cancer, it is designed to protect against the type of HPV associated with the malignancy.
"This adds more data that HPV is an important cause of cancer and that this is an important vaccine," said Joseph Bocchini, who chairs the American Academy of Pediatrics' committee on infectious diseases.
The type of oral cancer linked to HPV strikes about 11,000 Americans each year. About the same number of women each year are diagnosed with cervical cancer.
The new finding could spur calls to vaccinate both boys and girls, because oral cancer strikes both.
"This will reinvigorate and shift the debate about who should get vaccinated," said Robert Haddad of the Dana Farber Cancer Institute.
Proponents of the vaccine have been advocating mandatory vaccination of girls, sparking an intense nationwide debate. Opponents say the vaccine may encourage sexual activity and that the vaccine is too new to know for sure that it is safe and its effectiveness is long-lasting. They argue that the decision should be left to parents.
It remains unclear whether kissing someone who is HPV-positive poses any risks, Gillison said.