10 May 2007

HPV Now Implicated In Throat Cancers

by Kate Melville

As well as cervical cancer, HPV has now been linked to throat cancer; with researchers from the Johns Hopkins Kimmel Cancer Center claiming that oral HPV infection is the strongest risk factor for HPV-linked cancer - regardless of tobacco and alcohol use.

Reporting their findings in the New England Journal of Medicine, the researchers noted that having multiple oral sex partners tops the list of sex practices that increase risk for the HPV-linked cancer. While fellatio and cunnilingus are the main modes of oral HPV infection, the investigators said that mouth-to-mouth transmission was also possible.

As well as saliva, HPV strains can also be found in the genital tract, in urine and in semen. While most HPV infections clear with little or no symptoms, a small percentage of men and women who acquire "high-risk" HPV strains - such as HPV 16 - may develop oral, anal, cervical, vaginal, penile, or vulvar cancers.

It appears that the association between the virus and throat cancer is extremely strong, with HPV 16 being present in the tumors of 72 percent of oropharyngeal (located in the tonsils, back of the tongue, and throat) cancer patients enrolled in the study. The results showed that those subjects with newly diagnised oropharyngeal cancer who had evidence of prior HPV infection were 32 times more likely to develop the cancer. Additionally, the subjects who reported having more than six oral sex partners in their lifetime were 9 times more likely to develop the HPV-linked cancer.

Smokers and drinkers usually increase their throat cancer risk by around 3 times, but intriguingly, study author Maura Gillison said there appeared to be no added risk for HPV carriers who also smoked and drank alcohol. "It's the virus that drives the cancer," she explained. "Since HPV has already disrupted the cell enough to steer its change to cancer, then tobacco and alcohol use may have no further impact." Somewhat shockingly, Gillison expects the incidence of HPV-associated cancers to soon outpace those caused by tobacco and alcohol use.

Gillison noted that while the new HPV vaccine (Gardasil) can prevent genital HPV infection in girls and young women, it has not yet been shown to prevent oral infection, but studies in this area are planned for the future. For those who already have HPV-linked oropharyngeal cancer, there is some good news. Gillison's previous studies, along with others, showed that these patients have a survival advantage with most living well past the five-year mark.

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Source: Johns Hopkins Medical Institutions