The number of head and neck cancers linked to the sexually transmitted human papillomavirus (HPV) has increased sharply over the past two decades, and the virus now accounts for more cancers than tobacco or alcohol, a new study finds.
Researchers tested 271 cancer tissue samples collected from oropharyngeal cancer patients in Hawaii, Iowa and Los Angeles between 1984 and 2004. In 1984-89, about 16% of oropharyngeal cancers — cancers of the tonsils, upper throat and base of the tongue — tested HPV-positive, the researchers found. By 2000-04, the proportion of HPV-positive cancers had risen to 72%.
That means that the rate of HPV-related oral cancer rose from 0.8 cases per 100,000 people in the 1980s to 2.6 cases per 100,000 people in the 2000s — an increase of 225%. At the same time, as cigarette smoking declined, the rate of HPV-negative cancers dropped by 50%, the study found.
Overall, the risk was greatest and rising in men, and the findings suggest that it may have to do with an increase in oral sex. “We believe that sexual habits have changed, and that there is an increase in sexual activity earlier on in life, with an exchange of many more sex partners in general,” Dr. Tina Dalianis of the Karolinska Institute in Sweden, who wasn’t involved in current study but has conducted previous research on HPV-related oral cancer, told Reuters Health.
HPV is best known as the virus that causes cervical cancer in women, but because of better screening, the rate of such cancers has declined over time. The authors predict that if current trends continue, oral cancers may become the most common HPV-related cancer by 2020, eclipsing cervical cancer.
“The burden of invasive HPV-caused cancers will shift from women to men in the U.S., largely due to the rise of HPV-positive oropharynx cancers among men,” study senior author Dr. Maura Gillison of the Ohio State University Comprehensive Cancer Center in Columbus told CNN.
The good news is that patients with HPV-positive oral cancers have better survival rates than those with cancer due to other causes, possibly because their tumors have less genetic damage, which makes them more responsive to treatment.
“The HPV status of a patient’s tumor is the single greatest determinant of whether a person lives or dies after a diagnosis of local-regionally advanced oropharynx cancer,” said Gillison. “HPV-positive patients have an approximate 60% reduction in risk of death after their diagnosis when compared to HPV-negative patients.”
Most HPV-related oral cancers are caused by HPV 16, a strain that is targeted by the HPV vaccines Gardasil and Cervarix. Vaccination is currently recommended for girls and women to protect against cervical cancer, and the vaccine is also approved for boys to protect against genital warts and anal cancer.
Whether the vaccine could help prevent oral cancer is unknown, but experts speculate that if the vaccine results in fewer HPV infections in women, it could in turn help reduce the rate of infections in men.
The research was published in the Journal of Clinical Oncology.