NEW YORK — A virus spread by oral sex may cause more cases of throat cancer in men than smoking, a finding that spurred calls for a new large-scale test of a drug used against the infection.
Researchers examined 271 throat-tumor samples collected over 20 years ending in 2004 and found that the percentage of oral cancer linked to the human papillomavirus, or HPV, surged to 72 percent from about 16 percent, according to a report released Monday in the Journal of Clinical Oncology. By 2020, the virus-linked throat tumors — which mostly affected men — will become more common than HPV-caused cervical cancer, the report found.
HPV is known for infecting genitals. The finding that it can spread to the throat and cause cancer may increase pressure on Merck, the second-largest U.S. drugmaker, to conduct large-scale trials to see if its vaccine Gardasil, which wards off cervical cancer in women, also prevents HPV throat infections.
“The burden of cancer caused by HPV is going to shift from women to men in this decade,” Maura Gillison, an oncologist at Ohio State University and study senior author, said in a telephone interview. “What we believe is happening is that the number of sexual partners and exposure to HPV has risen over that same time period.”
Gillison said she worked with researchers at Merck several years ago to design a study in men. After Merck acquired Schering-Plough Corp. in 2009, though, the trial “was canceled,” she said.
Pamela Eisele, a spokeswoman for Merck, said the company decided not to move ahead with a big oral cancer study “due to competing research and business priorities.” GlaxoSmithKline has “no plans” to study the company’s competing vaccine Cervarix outside of cervical cancer, Jennifer Armstrong, a company spokeswoman, said in an email.
Gardasil is approved for preventing cervical, vaginal and anal cancers and genital warts, and is recommended for girls and women ages 9 through 26. It is also approved for preventing genital warts and anal cancer in boys and young men of the same ages. Glaxo’s Cervarix is approved for preventing cervical cancer in females ages 9 through 25.
Both vaccines target the HPV strain linked to oral cancer, Gillison said.
HPV-linked throat cancers, or orophyaryngeal cancer, are increasing so rapidly that by 2020 there will be 8,700 U.S. cases, with 7,400 cases in men, versus 7,700 cases of cervical cancer, the study said. Male cases alone will outnumber cervical cancer cases soon after 2020, Gillison said. The Ohio State study is based on tumor samples from several states.
Roughly 20 million Americans have genital HPV infections, according to the Atlanta-based Centers for Disease Control and Prevention. At least half of sexually active women and men get it at some point in their lives, the CDC says. Most of the time it doesn’t cause health problems.
Until recently, head and neck cancer mainly occurred in older patients and was associated with tobacco and alcohol use. The HPV-linked head and neck cancers, usually of the tonsils, palate or tongue, hit men their 30s, 40s, and 50s, Gillison said. It is unclear why women are affected much less often than men, she said.
Gillison started researching the oral cancer epidemic more than a decade ago as a fellow at Johns Hopkins University. Another researcher told her about a report from Europe of a case of oral cancer that was HPV positive, she said.
“I started working on it immediately,” she said.
In a 2007 epidemiology study published in the New England Journal of Medicine, Gillison and her colleagues found that having a high number of oral or vaginal sex partners are risk factors for HPV-associated throat cancer. The cancer may also be spread by open-mouth kissing, Gillison said in the interview.
“Nobody paid attention to oral HPV infections until 2007,” she said. “We are about 15 years behind in the research” compared with the data on cervical cancer and HPV, she said.