Oral Sex Is Major Risk Factor
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Having multiple oral sex partners topped the list of practices associated with an increased risk of developing oropharyngeal cancer, according to the study published in the May 10 issue of The New England Journal of Medicine.
People in the study who reported having a history of six or more oral sex partners were three times as likely to develop the cancer as people who reported that they had never had oral sex.
In looking at patients with tumors that were positive for a particular strain of HPV already well-linked to cervical cancer, six or more oral sex partners increased risk for throat cancer by eightfold.
And those who showed evidence of a prior oral infection with human papillomavirus (HPV) were 32 times more likely to develop the cancer.
Oral sex seemed to be the main mode of transmission for oral HPV, although the researchers note that transmission from mouth to mouth contact couldn't be excluded. The new study shows that oral HPV infection is linked to head and neck cancer regardless of two other known risk factors: heavy tobacco and alcohol use.
But longtime HPV researcher Maura L. Gillison, MD, PhD, of Johns Hopkins University in Baltimore, says the findings should not be seen as cause for undue alarm.
"This is a very uncommon cancer, so a person's individual risk is pretty small," she tells WebMD.
Sex, Smoking, and Alcohol
Gillison and colleagues first reported the link between oral HPV infection and head and neck cancer in 2000, and since then dozens of other studies have bolstered the finding.
But their latest investigation is among the first to comprehensively examine the behaviors that contribute to risk.
Longtime heavy tobacco and alcohol use are among the strongest identified risk factors for head and neck cancers.
But the new findings suggest that HPV is a stronger risk factor for oropharyngeal cancer, which Gillison says accounts for about one in four head and neck cancers. Oropharyngeal cancer occurs in the area beyond the mouth from the base of the tongue to the back of the throat.
"The number of oropharyngeal cancers caused by HPV is probably larger than the number caused by smoking and alcohol, at least in the U.S.," Gillison says.
The new research included 86 men and 14 women with a new diagnosis of oropharyngeal cancer and 200 sex- and age-matched people without cancer.
Both groups completed anonymous surveys examining sexual history and other lifestyle factors, and oral swabs, blood, and saliva samples were collected from all participants.
HPV 16, one of two HPV strains that cause 70% of cervical cancers and 90% of head and neck cancers that are HPV-positive, was found in 72% of the oropharyngeal tumors. Evidence of prior HPV 16 exposure, in the form of antibodies to the virus, was also strongly linked to oropharyngeal cancer.
The researchers were also surprised to find that heavy smoking and drinking did not seem to add to the risk in people with evidence of oral HPV infection.
Vaccination's Role Unclear
It is not yet clear if the HPV vaccine now approved for the prevention of cervical cancer in women can also prevent HPV-driven throat cancer or other malignancies that have been linked to HPV infection, including those of the anus, vagina, and penis.
"There is every reason to believe that it will, but we don't know that yet," Gillison says.
Debbie Saslow, PhD, of the American Cancer Society tells WebMD that if the vaccine is proven safe and effective in boys and young men, the indications for its use will grow.
"It is everybody's hope that the vaccine will eventually decrease the incidence of many types of cancer," she says.
Gillison says the main message from the current research is to doctors who may not suspect head and neck cancer in patients without a history of heavy smoking and drinking.
"This expands our idea of who might be at risk for head and neck cancers," she says. "There is a proven survival benefit to catching these cancers early, so recognizing that people without traditional risk factors may still be at risk is important."
SOURCES: D'Souza, G. New England Journal of Medicine, May 10, 2007; vol 356: pp 1944-1956. Maura L. Gillison, MD, PhD, assistant professor of oncology and epidemiology, Johns Hopkins University, Baltimore. Debbie Saslow, PhD, spokeswoman, American Cancer Society.
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