Human papillomavirus (HPV) infections multiply the risk of certain head and neck cancers, particularly those of the tonsils, researchers report.
There are dozens of HPV variants, many of which are harmless, says study leader Jon Mork of the National Hospital in Oslo. Some HPV is sexually transmitted and is commonly blamed for genital warts.
But the scientific case for HPV infections as the cause of some cancers has been mounting. The strongest evidence so far comes from studies that link several specific virus types, including HPV-16 and HPV-18, to cervical cancer (SN: 6/13/98, p. 382). Other studies have also found HPV-16 particles in prostate tumors (SN: 2/27/99, p. 135).
Evidence for a possible HPV connection to head and neck cancers has been building, too. Last year, for example, researchers found that HPV-16, which might be transmitted through oral sex, was present in tumor cells in people’s mouths and throats. However, the study did not show that the virus actually causes these cancers, according to some researchers. They argue that finding HPV in tumor cells could be the result of such cells’ becoming more vulnerable to HPV infections.
In an attempt to clarify the connection, Mork and his coworkers searched through cancer registries in Norway, Finland, and Sweden. They identified 292 people who had developed head and neck cancer and had donated blood samples from 1 month to 20 years before they were diagnosed with the disease.
Mork’s team then analyzed the stored blood samples to determine how many of the individuals had been infected with the virus before their cancer diagnosis and which type of HPV was present in these people’s blood. The team did similar blood tests on 1,568 cancer-free people.
After compensating for heavy smoking, which influences cancer risk, the researchers found that HPV-16 infections doubled the risk of developing head and neck cancer and increased the risk of cancer in the tonsils and surrounding tissue 14-fold. Infection with three other types of HPV linked to other cancers did not increase the risk of any head and neck cancer.
Mork and his colleagues report their findings in the April 12 New England Journal of Medicine.
This study provides the “first evidence” that infection with HPV-16 places people at risk for developing head and neck cancers, particularly those of the tonsils, says Maura L. Gillison, a medical oncologist at the Johns Hopkins University Medical Institutions in Baltimore.
Some researchers remain skeptical. Gershon J. Spector, a head and neck surgeon at Washington University in St. Louis, says this study “doesn’t tell you anything about cause and effect.” Without that knowledge, researchers can’t develop effective treatments for head and neck cancer by targeting HPV, he says.
By showing that HPV infection precedes the cancer diagnosis, Mork contends, he and his colleagues have strengthened the hypothesis that HPV can cause head and neck cancer. He concedes that such a claim requires more experimental backing, but he says, “the picture is getting clearer.”