Virus Spread by Oral Sex Is Linked to Throat Cancer
Thursday, May 10, 2007
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 100 people with throat cancer and 200 without it, found that those infected with the human papillomavirus were 32 times as 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 L. 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 rates of oral cancer have been increasing in recent years, particularly among younger people and those who are not smokers or heavy drinkers, which had long been the primary at-risk groups, experts said.
"There's been a kind of sea change in the last 10 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 contradicts widespread misconceptions about oral sex.
"Many adolescents, and adults too, say they engage in oral sex as a less risky type of sex," said Mark A. Schuster of Rand Corp. and UCLA, noting that herpes, syphilis, gonorrhea, HIV and other sexually transmitted infections can 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 whether 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 A. Bocchini Jr., 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, which is about the same as the number of women in whom cervical cancer is diagnosed.
The finding could also spur calls to vaccinate boys as well as girls because oral cancer affects both.
"This will reinvigorate and shift the debate about who should get vaccinated," said Robert Haddad of the Dana Farber Cancer Institute in Boston.
Proponents of the vaccine have been advocating mandatory vaccination of girls, sparking an intense nationwide debate. Opponents say that the vaccine may encourage sexual activity and that its safety and long-term effectiveness are not clear because it is so new. They argue that the decision should be made by parents individually.
Two other studies published in the same issue of the journal found that the vaccine's protection against genital warts and precancerous growths lasts at least three years. Such growths can lead to cervical cancer.
Gillison and her colleagues focused on a type of tumor called oropharyngeal cancer -- cancer of the tonsils and surrounding tissue. It usually can be treated with surgery, radiation and chemotherapy, but patients can be left with dry mouth and difficulty speaking and swallowing.
The researchers tested 100 people with the cancer and 200 similar subjects without it for HPV infection either anywhere in the body or specifically in the mouth. Researchers also examined factors that would influence the subjects' chances of being infected with the virus or developing the cancer, such as their sexual histories and whether they smoked or drank alcohol.
After other factors were considered, those who tested positive for HPV were 32 times as likely to have oropharyngeal cancer.
When researchers looked at sexual history alone, the number of partners emerged as a risk factor for developing the cancer. Those subjects who had had one to five oral-sex partners were 3.8 times as likely as those with fewer oral-sex partners to have it, whereas those who had more than six oral-sex partners were 8.6 times as likely. It made no difference whether the partners were male or female.
It remains unclear whether kissing someone who has HPV poses any risks, but "it is not out of the realm of possibility," Gillison said.