Sixteen, Going on HPV 16

Human papillomavirus (HPV) infection is responsible for causing cancer at more than one site of the body, including the mouth and throat, anus, and penis in men; and the mouth and throat, anus, cervix, vagina, and vulva in women. Between 2008 and 2012, the most common cancer was oral squamous cell carcinoma, of which there were 3,100 cases in women and a much higher 12, 638 in men.

And while a few PT bloggers have written of the oral sex-oral cancer nexus, the depth of the origins of this public health crisis has not been explored as thoroughly as we chroniclers of ill-fated oral love would like—until now.

A recently published study in the Annals of Internal Medicine appears to have succeeded in illuminating why the incidence of HPV-positive oral cancer is so high among men, and if there is a concordance of oral and genital HPV infection.

The researchers found that the prevalence of high-risk oral HPV infection in the United States is substantially higher in men than women. To be precise, they found that 7.3 percent of men and 1.4 percent of women in the general population have high-risk oral HPV infection, which equates to 7 million men and 1.4 million women, respectively. In particular, the prevalence of HPV 16, a particularly dangerous HPV type known to contribute to increased risk for oral cancer, is six times greater in men than women, equating to 1.7 million men and 0.27 million women with HPV 16 infection.

Further, it was found that the prevalence of oral HPV infection was high among men with concurrent genital HPV infection. This finding is particularly important given the recently reported high prevalence of genital HPV infection (45.2 percent) among U.S. men. Earlier studies have shown oral and anal concordance among men who have sex with men; individuals were more likely to have any oral HPV if they also had any anal HPV.

The association between sexual behaviors (such as number of sex partners) and the high prevalence of oral HPV infection among adults with genital HPV infection observed in the study implies that transmission via genital-oral sex may be occurring in this group—something we all “knew.” However, oral HPV infection likely is also acquired via auto-inoculation from genital HPV infection, or vice versa, through, say, fingers or adult “toys” in the same individual.

Careful study of HPV transmission dynamics is crucial—not just a puerile inquiry into what some may interpret as titillating sexual preferences—because the bidirectional transmission between genital and oral HPV likely is promoting HPV-related cancer in the same individuals, and even contributing to the increased risk of second primary HPV-related cancer in men—for example, separate diagnoses of anal and oral cancers.

Differences in the burden of oral cancer-associated infection and the development of oral cancer among men and women appears at least partially explained by the strength of association between sexual behaviors and HPV infection among men, and a higher prevalence of HPV 16 infection in men.

Researchers also examined risk factors for oral HPV infection. They observed a dose-response association between oral HPV prevalence and cigarette use. In addition, the predicted probability of oral HPV infection was greatest among participants who had 16 (that number again) or more lifetime oral sex partners. The authors of the paper found this to be consistent with a previous study showing that persons who have had many oral sex partners have greater odds of oral HPV infection.

Considering the conclusions—that overall prevalence of oral HPV infection was high among U.S. men, and that approximately 2 million men had infection with the cancer-causing strain, HPV 16, and that the overall oral HPV infection prevalence was particularly high among men who have had many (>16) lifetime oral sexual partners (29.8 percent), or reported having sex with men (18.2 percent), or were suffering concurrent genital HPV infection (19.3 percent)—we can only hope that public-health experts will improve targeted prevention and advances in screening and early detection procedures to combat oral—and other—cancers in those high risk HPV-infected individuals.