Oral cancers like the one actor Michael Douglas referenced in a recent newspaper interview are on the rise in the United States, and doctors say that about 10,000 cases a year could be prevented with safe and effective vaccines.
The star of HBO's "Behind the Candelabra" spoke about his throat cancer that was diagnosed in 2010 and its sometime association with the ubiquitous human papillomavirus, or HPV, and oral sex.
"Because without wanting to get too specific, this particular cancer is caused by HPV [human papillomavirus], which actually comes about from cunnilingus," today's edition of The Guardian newspaper quoted the 68-year-old actor as saying.
But the actor's publicist, Allen Burry, told ABCNews.com today that his client "never said it was the cause of his particular cancer. They did discuss it. He did say oral sex is a suspected cause of certain oral cancers. He did not say it was his specifically."
About 63 percent of the estimated 11,726 cases of oropharyngeal cancers diagnosed each year in the United States are thought to be caused by HPV, according to the Centers for Disease Control and Prevention. Another 3,000 Americans are diagnosed each year with HPV-associated anal cancer and the rate of infection appears to be increasing.
"Right now in the United States only 2 percent of boys are vaccinated, which is shocking because by the time they are adults, these boys will be more likely to get cancer from HPV than girls," said Dr. Kevin Cullen, director of the University of Maryland's Marlene and Stewart Greenebaum Cancer Center.
"By the time they become adults, throat cancer from HPV in men is four times more likely than cervical cancer in women."
HPV spreads via oral, vaginal and anal intimacy, as well as through cunnilingus and fellatio. The virus does not live in the blood, semen or vaginal secretions. It takes about 20 years for exposure to the virus to develop into cancer.
Doctors say that changing sexual behaviors -- earlier sex, more partners and especially oral sex -- are contributing to a new epidemic of orpharyngeal squamous cell cancers, those of the throat, tonsils and base of the tongue.
Similarly high rates have also been seen in Europe, where a 2010 Swedish study showed a strong correlation between oral cancers and oral sex.
About 50 percent of all girls are vaccinated against HPV-related cervical cancer, a number which is slowly increasing because of strong CDC recommendations, Dr. Cullen said. Women do get HPV-related throat cancer, but at a much lower rate than men.
"The take home message is this virus is out there and virtually everyone is exposed as they become sexually active ... no matter what point in life," he said. "And boys are at greater risk than girls."
The CDC recommends two licensed vaccines, Gardasil and Cervarix, to protect against cervical, anal and oral cancers, but those guidelines have never been fully embraced by parents or young adults.
"Why not prevent what's preventable? HPV infects both sexes," Austin, Texas, pediatrician Dr. Ari Brown said. "And, while the biggest benefit for boys to get this shot is prevention against spreading it to girls, boys are at risk for other types of HPV-related cancers as well as genital warts."
But even as HPV-related head, neck and throat cancers are on the rise -- by more than 225 percent between 1988 and 2004, according to one study in the Journal of Clinical Oncology -- vaccination rates remain low.
"I think the public was spooked and once people are scared, it is hard to unscare them," Brown said. "However, the vaccine has been out for seven years now. Over 40 million doses have been given. Hopefully, people will become more accepting of the vaccine over time and we will be able to reduce the number of illnesses caused by HPV."
About 79 million Americans are infected with HPV and about 14 million become newly infected each year, according to the CDC. The virus is so common that nearly all sexually active men and women will get at least one kind of HPV in their lifetimes.
Cervarix is recommended for females 10 through 25 years of age. Gardasil is recommended for 11- and 12-year-old girls, and also females 13 through 26 who were not previously vaccinated. It is also for 9- through 26-year-old males.
Some parents have objected to giving their sons and daughters a vaccine that presumes they will be sexually active.
"What I always tell parents is that you don't have to have intercourse to get HPV," Dr. Brown said. "There are other forms of intimacy that can spread this virus. So, just because you believe your child will not have sex until they are 30 or married, etc., it is possible that having a physical relationship with a partner will lead to HPV infection."
The virus can be spread via skin-to-skin contact with an infected partner, although thin genital skin is the most easily infected.
Others have expressed safety concerns about the vaccine.
A government report released in 2009 linked Gardasil to 32 unconfirmed deaths, as well as incidents of blood clots and neurological disorders.
Cullen said looking back at reports, researchers have concluded that there were "no excess deaths" directly attributed to the vaccine.
"The vaccine has been given to hundreds of thousands, if not millions worldwide," oncologist Cullen said. "We have more than 10 years experience and it has been looked at carefully. We can now say with complete confidence that it is very safe and the reactions we have seen are usually very mild, as you would see with any injection."
Because of the growing acceptance of vaccination among girls, cervical cancer rates among women are beginning to decline, Cullen said. "All this is very good news," he added.
But HPV rectal and anal cancers are "going up significantly."
Each year, more than 30,000 new cases of cancer of the oral cavity and pharynx are diagnosed, and more than 8,000 people die from oral cancer, according to the CDC.
There are more than 100 strains of the virus. Some cause genital warts, but others can result in cell changes that decades later can become cancerous. Each strain is identified by a number; oral and cervical cancers are caused by HPV sub-types 16 and 18.
HPV can also cause cancers of the vulva, vagina and penis, and there is some evidence it is associated with lung cancers.