WASHINGTON, D.C – Teens tend to view oral sex as less risky than "real" sex, but it's far from inconsequential, researchers say. There is growing evidence that oral sex increases the risk of some head and neck cancers.

Studies have shown that the more oral sex partners a person has, the higher their risk of developing cancer of the oral cavity or the pharynx, which is the upper part of the throat, said Dr. Maura Gillison of Ohio State University, who studies head and neck cancer and its link with human papilloma virus (HPV).

Oral sex may also be a "gateway" to vaginal intercourse, with most sexually-active adolescents reporting that they began having vaginal sex within six months of engaging in oral sex, Gillison said.

Public health professionals should be aware of teens' attitudes towards oral sex, and educate and council them about the risks.

"I see most of the health policies out there and guidelines for preventive services talking about sex generally, but they do not specify oral sex," said Bonnie Halpern-Felsher, a professor of pediatrics at the University of California, San Francisco. "That is an important distinction, because teens don't consider oral sex to be sex, and many are not aware of the risks involved," Halpern-Felsher said.

Halpern-Felsher and Gillison, along with other experts in the field, spoke today about the risks of oral sex for teens here at the annual meeting of the American Association for the Advancement of Science.

Oral sex and cancer

HPV is commonly associated with cervical cancer. The virus causes more than 90 percent of all cases of that disease. The virus infects the skin and mucosal tissues, and is spread by human-to-human contact.

But the virus has also been linked to some head and neck cancers, Gillison said. About 64 percent of oral cancers in the United States show evidence of HPV infection, she said. And oral cancers positive for HPV occur more frequently in younger individuals, according to the Oral Cancer Foundation.

HPV was first implicated as the cause of some oral cancers in 2000. Since then, researchers have examined the link between sexual behavior, including oral sex, and the risk of oral cancer, Gillison said.

One study found that people who had performed oral sex on six or more partners in their lifetime had an eight-fold increased risk of cancers of the mouth or throat, compared with those who had never performed oral sex, Gillison said.

In addition, studies have shown that oral sex is strongly associated with HPV-positive cancers, but not with HPV-negative cancers, Gillison said.

However, more research needs to be done to map out the sequence of events linking HPV to oral cancer. Researchers first need to show that oral sex increases the risk of HPV infection, and then that HPV infection increases the risk of oral cancer, Gillison said.

It's too soon to say whether an HPV vaccine could protect against oral cancer, Gillison said. However, it's possible that a vaccine might be more effective at preventing oral cancer than the two approved vaccines are at preventing cervical cancer. That’s because nearly all cancers of the mouth or throat caused by HPV are due to one strain of the virus, called HPV-16, Gillison said. In contrast, two strains of HPV account for about 70 percent of cervical cancers.

Teens and oral sex

In a recent study, Halpern-Felsher and her colleagues surveyed more than 600 high school students about their sexual behavior, every six months from 2002 to 2005.

Teens who engaged in oral sex in ninth grade had a 50 percent chance of having vaginal sex by the end of eleventh grade, the researchers said. In contrast, those who began oral sex in the eleventh grade had only a 16-percent chance of having vaginal sex by the end of that year.

The study will be published in the March issue of the journal Archives of Pediatrics and Adolescent Medicine.

Previous work by Halpern-Felsher and colleagues found that adolescents think of oral sex as less risky, emotionally and physically, than vaginal sex. Close to 14 percent of adolescents think that oral sex doesn't come with any health risks, Halpern-Felsher said.

"We need to make sure teens know that if they do choose to have oral sex, certainly it does involve less risk than intercourse, but it's not risk-free," Halpern-Felsher said. "We also have to be sure to ask teens if they have any questions. It sounds simple, but it is a very important step that parents and health care providers should be taking."

Pass it on: Teens don't think of oral sex as sex, and believe that it has fewer risks. However, there is increasing evidence that oral sex may increase the risk for some types of head and neck cancers.

Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner.