By Andy Blatchford, The Canadian Press

MONTREAL — Amid Michael Douglas’s personal and philanthropic battle with throat cancer, the Oscar-winning actor is shedding light on a viral form of the disease lurking in a growing number of mouths.

Oral cancer has long been linked to tobacco and alcohol use, but an expanding body of research suggests human papillomavirus, or HPV, is an increasing cause of the deadly disease.

The culprit behind the sexually transmitted virus’ emergence in mouth and throat cancers? Experts say a major factor is the prevalence of oral sex.

More and more researchers have cast their microscopes on the mysteries of HPV-caused oral cancers, including McGill University, which received a big fundraising boost last week with the help of Douglas.

The grateful actor, diagnosed with throat cancer last year in a Montreal hospital, volunteered to headline a charity event for the McGill Head and Neck Cancer Fund.

The 66-year-old, who calls himself a “poster boy” for head-and-neck cancer, has blamed alcohol as a likely source of his illness, not HPV.

Still, a portion of the $2 million amassed at the event will support HPV-caused oral cancer research.

The doctor who first detected the walnut-sized tumour in Douglas’s throat said the fund has supported HPV projects in the past and more are in the works.

“This is an area of increasing incidence,” Dr. Saul Frenkiel said of HPV-caused oral cancer at the university-affiliated hospital where he treated Douglas.

Although relatively rare, the Canadian Cancer Society estimates oral cancers, in general, caused 1,150 deaths last year in Canada.

The group says there were around 3,400 new cases of oral cancer in 2010, making it the 13th most common type of cancer in the country. Prostate cancer ranked No. 1 with 24,600 new cases.

Researchers and physicians say HPV has increasingly played a bigger role.

Dr. Eduardo Franco, McGill’s director of cancer epidemiology, has studied HPV-linked cancers for more than 25 years, and estimates the virus is the source of between 25 and 35 per cent of oral cancer.

He said effective anti-smoking campaigns have helped reduce tobacco-related oral cancers by about two per cent a year since 1997.

But the number of cases of oral cancers has remained steady, he added.

“The reason why for so long we distrusted this potential new cause of oral cancer was because we seemed to know pretty well what caused oral cancer — namely tobacco smoking and alcohol consumption,” he said.

Franco said research into HPV-related oral cancer really only began in the 1990s and the technique to identify viral DNA is relatively new, meaning outside of specific studies, statistics on the overall increase have been difficult to compile.

He said oral sex has become more prevalent since the 1960s, boosting the spread of HPV to mouths and throats — including strains known as potential causes of cancer.

“This was a period of tremendous social changes and liberal attitudes and to more hedonistic ways of looking at life,” he said.

On the positive side, Franco said HPV-caused oral cancers are more treatable than the non-viral ones.

Dr. Anthony Nichols, a head and neck surgeon in London, Ont., cited a 2009 Swedish study that found cases of at least one form of HPV-related cancer have tripled since 1970.

“The number is definitely increasing worldwide,” the London Health Sciences Centre doctor wrote in an email.

Nichols said studies have shown that HPV now causes nearly two-thirds of oral cancers, with the number of cases increasing by about two to three per cent per year.

“Which is a lot in cancer terms,” he said.

A 2008 U.S. study published in the Journal of Clinical Oncology categorized some 46,000 cases reported between 1973 and 2004 and found that incidence rates for HPV-linked oral cancers were on the rise.

At the time, study co-author Dr. Maura Gillison of Johns Hopkins University in Baltimore, Md., predicted the number of oral cancers in the U.S. caused by HPV to surpass those triggered by alcohol and tobacco within a few years.

Brian Hill, founder of the non-profit Oral Cancer Foundation in Los Angeles, said recent research shows it has already reached around 60 per cent.

Hill, who survived HPV-caused oral cancer, said safe oral sex doesn’t guarantee the virus won’t spread.

And good luck trying to get people to abstain from oral sex, he added.

“Let’s be realistic. You can’t say, ‘Don’t engage in oral sex,'” he said. “Everybody engages in oral sex. This isn’t some kind of abnormal behaviour.”

Doctors believe the HPV vaccine, currently offered to girls for the prevention of cervical cancer caused by the virus, could eventually prove itself as a protective method for oral cancer.

HPV is the leading cause of cervical cancer in women.

Health Canada approved the vaccine for use by girls and women in 2006 and it has become part of many school-based immunization campaigns. In February 2010, Health Canada also approved the vaccine for boys and men ages nine through 45.

Franco said boys should be inoculated against HPV.

“I’m a strong believer in the value of HPV vaccination,” said Franco, adding he expects the high cost of the vaccines will decrease over time.

“I’ve conducted these clinical studies, I’ve advised the pharmaceutical companies of the best ways to conduct these trials, I’ve seen the results.”

Another preventative measure for oral cancers is screening, something Douglas endorsed in his speech last week in Montreal.

Douglas noted that Sunday was the start of oral, head and neck cancer awareness week, when U.S. hospitals are offering free screenings for the disease.

But Douglas, who saw several doctors before his cancer was detected, explained that even checkups offer no guarantee.

Frenkiel believes the quality of oral examinations will only improve.

“I think it’s a way of the future, absolutely,” he said.

“There’s going to be new technologies emerging for screening … in the oral cavity.”