Oral human papillomavirus infection more likely to persist in older men

Oral infection with human papillomavirus 16 (HPV16), which is the type of HPV most frequently linked to HPV-driven head and neck cancers, was more likely to persist 12 or more months in men older than 45 than in those younger than 45, according to a study published in Cancer Prevention Research, a journal of the American Association for Cancer Research.

"Oral HPV16 is the HPV type most commonly found in HPV-driven oropharyngeal cancers, which have been increasing in incidence recently in the United States," said Christine M. Pierce Campbell, PhD, MPH, an assistant member in the Department of Cancer Epidemiology and Center for Infection Research in Cancer at the Moffitt Cancer Center in Tampa, Florida. "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.

"Our results show that some oral HPV16 infections persist in men for four years or more and that persistence seemed to increase with age," continued Pierce Campbell. "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.

"Unfortunately, there are currently no methods to detect precancerous lesions of the head and neck," Pierce Campbell added. "So, before our data can be translated for patient benefit, we need more studies of HPV-related head and neck cancers to develop screening methods that may be useful in a clinical setting."

Pierce Campbell and colleagues analyzed oral samples from 1,626 men participating in the HPV Infection in Men (HIM) Study, an ongoing, multi-national cohort study of the natural history of HPV infections in men. Oral samples were collected at enrollment and then every six months for up to four years.

Over the course of the study, HPV16 was detected in two or more oral samples from 23 men. For 10 men, it was present in the sample collected at enrollment. Infections present at the start of a study are called prevalent infections while those that arise during the study are called incident infections.

Among the 10 prevalent 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, four lasted one year or longer, one lasted two years or longer, and none lasted three or more years.

The proportion of incident infections persisting for one year or longer increased with age. All incident infections among men older than 45 persisted for one year or longer, 50 percent of those infections among men ages 31 to 44 persisted for one 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," said Pierce Campbell. "Prevalent infections are likely to have been present for a while, increasing the likelihood that they will be persistent."

Funding for the study was provided by Merck Sharp & Dohme, the American Cancer Society, and the National Cancer Institute Intramural Research Program. The infrastructure of the HIM Study cohort was supported through a grant from the National Cancer Institute. Pierce Campbell declares no conflicts of interest.