The sexually transmitted virus that causes cervical cancer in women has now been linked to an uptick of throat, tonsil and tongue cancers - in a younger and healthier group of patients than doctors have ever seen before.
These head and neck cancers were once the scourge of older men - mostly the result of lifetimes of heavy smoking and drinking. The treatments often left victims disfigured.
But with those cases on the decline, doctors are seeing a new group of victims. They're men in their 40s, and even 30s, whose cancer is brought on by the increasingly common human papillomavirus (HPV). It's an infection that more than half of Americans will encounter during their lifetimes. And researchers now believe that the increase in certain oral cancers can be traced to the spread of the virus through oral sex.
New studies suggest that HPV-related oral cancer cases are on pace to eventually surpass cases of cervical cancer in the United States, which strikes about 11,000 women each year. And many doctors do not realize that they should be on the lookout for oral cancer in younger patients.
"It just kind of rocks the whole paradigm," said Dr. Maura Gillison, a Johns Hopkins oncologist who is credited with making the link between HPV and oral cancers. "Everyone thinks of the long-term smoker, the long-term drinker. Now we're seeing the movers and shakers in the prime of life."
Gillison and others say they hope an HPV vaccine designed to protect girls and young women against cervical cancer will be approved for boys and tested for head and neck cancers, which are more likely to affect men than women.
Researchers say changing sexual behavior probably accounts for the explosion of HPV-related oral cancers. In a study published last year in The New England Journal of Medicine, Gillison and colleagues found the strongest link in patients with larger numbers of lifetime sex partners.
The sexual revolution of the 1960s made it more acceptable to have more sex partners, she and others said. And, if the AIDS scare of the 1980s persuaded many to have safer sex, the caution didn't always extend to oral sex. The bottom line: more HPV-related oral cancers.
A reluctance to discuss oral sex may be why the public knows so little about the link between HPV and head and neck cancers.
There is plenty of open talk about preventing cervical cancer nowadays, including commercials that tout the blockbuster HPV vaccine with girls chanting about becoming "One Less." But there's still more of a taboo when it comes to talking about oral sex.
"The public is unaware of this," said Dr. Erich Sturgis, a head and neck surgeon at The University of Texas M.D. Anderson Cancer Center who has studied HPV. "It's just starting to filter out."
It doesn't even occur to some primary-care doctors that their patients younger than 60 might have developed oral cancer, but researchers say a lingering sore throat or a lump in the neck could be symptoms of the disease and should be checked out.
These cancers remain relatively rare, despite a 5 percent increase in cases each year since 2000. Estimates put cases of HPV-associated head and neck cancers at 6,000 per year - and cervical cancer cases at fewer than 11,000.
Debbie Roffman, a human sexuality educator at Park School and author of Sex and Sensibility: The Thinking Parent's Guide to Talking About Sex, discusses risky behaviors with her students, some of whom are in middle school. But sometimes it's hard to get the message through, especially when students are sure those behaviors won't hurt them.
"They're not going to be as focused on invisible things like germs and long-developing things like cancer that are way off in the future," she said.
Gillison said everyone involved - from pre-teens to primary-care doctors - must change their perception of who is at risk. Doctors taking medical histories typically ask about smoking- and alcohol-related behaviors, but she said they should ask about sexual history, too.
"Now most of us are at risk, because humans are sexual beings," she said.
The rise of HPV-related head and neck cancers is not just a U.S. phenomenon. Swedish researchers who re-examined samples from the 1970s have found that 28 percent of oral tumors were HPV-positive. In tumors from 2000 to 2002, HPV-positive samples jumped to 68 percent.
In a study by Gillison and others last year, 72 percent of certain oral cancers were HPV-positive.
HPV is typically spread through sexual contact. While many women will have HPV at some point in their lives, they frequently have no symptoms and the virus usually goes away on its own. Sometimes, HPV lingers and becomes cancer - a process that can take decades.
Doctors are familiar with this progression because pre-cancerous lesions are often caught during Pap tests. But they don't know much about how progression occurs in the throat and mouth.
Gillison and her colleagues say HPV-related oral cancers appear to be distinct from those not associated with the sexually transmitted infection and appear to respond differently to treatment.
Two years after diagnosis, 95 percent of those with HPV-positive head and neck cancers were alive compared with 62 percent with HPV-negative cancers, research shows.
Even so, the treatment can have serious and long-lasting side effects. Some patients end up disfigured; others have difficulty speaking or swallowing. Gillison said those with HPV-positive tumors might be able to survive with less-damaging treatments.
Meanwhile, the HPV vaccine has been a financial boon for Merck & Co., the maker of Gardasil, the three-dose vaccine approved in the United States in 2006 for females ages 9 through 26. Doctors recommend vaccinating girls before they become sexually active and can be exposed to the virus.
Merck sold $1.5 billion worth of Gardasil last year around the world. GlaxoSmithKline is seeking U.S. approval for a competing drug called Cervarix.
Neither vaccine is approved for males. Both companies are studying whether it is safe in boys and whether it would prevent genital warts and rare cancers of the penis and anus. But neither has plans to study whether the vaccine would play any role in the prevention of HPV-linked oral cancers.
"Cervical cancer is really the focus," said Liad Diamond, a GlaxoSmithKline spokeswoman.
Experts said they think researchers will find the vaccine works on HPV throughout the body.
"The way the vaccine works, there's no reason to think it wouldn't protect against oropharanyx [tonsil, tongue and throat] cancer as it does cervical cancer," Sturgis said.
Dr. Aimee Kreimer, an epidemiologist at the National Cancer Institute in Bethesda, said that, theoretically, the vaccine should work on HPV anywhere in the body but such discussion is premature.
"Before recommending the vaccine to men, it's crucial to determine if the vaccination works to prevent infection in men," she said.