Oral HPV infection more likely to persist in older men

Oral infection with the human papillomavirus (HPV) type most frequently linked to HPV-related head and neck cancers (HPV16) is more likely to persist at least a year or more in men older than 45, according to a new study published in Cancer Prevention Research (January 9, 2015).

Oral HPV16 is most commonly found in HPV-driven oropharyngeal cancers, which have been increasing in the U.S.

"We don't know how long oral HPV infection must persist to increase risk for head and neck cancer, but we assume it would be similar to cervical infection, where it is generally believed that infections persisting beyond two years greatly increase the risk of developing cervical cancer," researcher Christine Pierce Campbell, PhD, MPH, said in a statement. Campbell is an assistant member in the department of cancer epidemiology and Center for Infection Research in Cancer at the Moffitt Cancer Center in Tampa, FL.

The researchers analyzed oral samples from 1,626 men participating in the HPV Infection in Men Study, an ongoing, multinational cohort study of the natural history of HPV infections in men. Samples were collected at enrollment, then every six months for up to four years.

HPV16 was detected in two or more oral samples from 23 men over the course of the study. It was present in the sample collected from 10 men at enrollment.

Among these 10 prevalent (present at the start of a study) infections, nine lasted one year or longer, eight lasted two years or longer, and two lasted for four years or longer. Among the 13 incident infections (those that arise during the study), four lasted one year or longer, one lasted two years or longer, and none lasted three or more years.

The researchers found that the proportion of incident infections persisting a year or longer increased with age. Among men older than 45, all incident infections persisted a year or longer. This is compared with half of those infections among men ages 31 to 44 persisted for a year or longer and none of the incident infections detected among men ages 18 to 31 persisted for one year.

"Our observation that prevalent oral HPV infections persisted longer than incident infections is consistent with what has been seen for cervical and anal HPV infections," Pierce Campbell said. "Prevalent infections are likely to have been present for a while, increasing the likelihood that they will be persistent."

Currently, there are no methods to detect precancerous lesions of the head and neck, Pierce Campbell noted. More studies are needed to develop screening methods, she said.

"Our results show that some oral HPV16 infections persist in men for four years or more and that persistence seemed to increase with age," Pierce Campbell said. "Genital HPV infections are generally cleared within two years, so our data show that oral infections may be more likely to persist than genital infections."

Funding for the study was provided by Merck Sharp & Dohme, the American Cancer Society, and the National Cancer Institute Intramural Research Program.

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