Head and neck cancer patients were once primarily older heavy smokers and drinkers. Now, the majority who are diagnosed with the disease are closer to middle age (many ages 40 to 55) and developed it not from years of tobacco or alcohol use but rather because they engaged in oral sex.
This shift has been traced to an increase in the human papillomavirus (HPV), the sexually transmitted infection that also causes cervical cancer. And oropharyngeal cancers are not the only malignancies the virus is spurring on. HPV is now likely responsible for more than 14,000 new cases of noncervical cancer in the U.S. each year.
Despite efforts to immunize more girls against HPV with the Gardasil or Cervarix vaccines—and continued debate about recommending the vaccine for boys—experts expect that number of these virus-linked cancers to continue to grow. "Based on what we have seen, in the past 10 years or so we don't see that the numbers have started to plateau," says Anil Chaturvedi, an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute. "They're still on the rise."
The virus is exceedingly common. In the U.S. at least half of those who are sexually active will get HPV at some point during their lives, and most carriers manifest no obvious symptoms, so people who are infected are usually unaware that they have it—and could be transmitting it to their partners.
Most infections, including some 90 to 95 percent of cervical HPV infections, seem to clear on their own within a couple years. But for people whose infection does not go away, they face a higher risk of cancer.
Clinicians currently have no standardized way to test for other types of HPV infection outside of the cervix, and the virus's progression to cancer remains somewhat of a mystery. "We know quite a lot about the natural history of the HPV infection of the cervix," says Maura Gillison, a professor of internal medicine and epidemiology at The Ohio State University Medical Center. But, for other sites, "there's very little information."
A new anatomy of infection
Cervical cancer is still by far the most common HPV-related cancer, causing about 10,800 new cases each year for 1998 to 2003. But a 2008 U.S. Centers for Disease Control and Prevention (CDC) assessment of the U.S.'s HPV-related cancer burden found that each year the virus also likely caused about:
• 7,400 cases (some 60 percent) of oral cavity and oropharynx cancer (5,700 in men; 1,700 in women)
• 3,000 cases of anal cancer (1,100 in men; 1,900 in women)
• 2,300 cases of vulvar cancer
• 800 cases (some 40 percent) of penile cancer
• 600 cases of vaginal cancer
During the course of the study period (1998 to 2003), the CDC found that the rates of HPV-associated oral cavity and oropharynx cancer steadily rose about 3 percent annually. Although these numbers might sound small, the change has not gone unnoticed by clinicians.
Greg Hartig, a surgeon and professor of otolaryngology at the University of Wisconsin–Madison, says that in the 15 years he has worked there he has seen a significant increase in the number of patients with HPV-positive cancers. Some 60 percent of oropharyngeal squamous cell cancers now show traces of HPV.
Many researchers estimate that HPV-positive cancer rates will continue to rise for at least the next decade or two. Why? Simple societal shifts: "This increase that we are seeing could be arising from changes in sexual behaviors that have occurred over time in the United States," Chaturvedi says. People seem to be having more types of sex with more people—and starting to do so at a younger age.
Several viruses, including hepatitis viruses and a herpesvirus, have been linked to cancers, but HPV is responsible for the highest number of virus-related malignancies. As a virus, however, it is highly unusual in that it can stick to a localized infection site, rather than spread throughout the body. "You can literally be at risk for cervical cancer and not at risk for oral cancer," Gillison explains.
This atypical infection pattern has meant specific sites in the body come under risk for cancer depending on an individual's sexual history. The virus can be spread through sexual contact and, some studies suggest, even kissing.