October 19, 2016 - 6:17 AM
TORONTO - Malignant tumours in the mouth and throat caused by the human papillomavirus have risen dramatically among men and could surpass the rate of HPV-induced cervical cancer in women, new statistics from the Canadian Cancer Society suggest.
In a report released Wednesday, the organization said the incidence of HPV-related mouth and throat cancers jumped 56 per cent in males and 17 per cent in females between 1992 and 2012, the latest year for which statistics are available.
An estimated 1,335 Canadian men and women were diagnosed with HPV-linked "oropharyngeal" cancers in 2012, and 372 died from the malignancies. They now represent about one-third of all HPV cancers in Canada, equal to the proportion of cervical cancer cases, said Leah Smith, the Canadian Cancer Society epidemiologist who helped author the report.
Human papillomavirus is the most common sexually transmitted infection worldwide. Most sexually active men and women become infected with HPV at some point during their lifetime. Most people clear the virus in about two years, but in a small proportion of those infected, the virus persists and can later cause cancer.
This year, almost 4,400 Canadian men and women will be diagnosed with an HPV cancer, including cervical, genital and anal cancers, and about 1,200 will die from their disease.
"HPV is a virus that infects moist skin, namely oral and genital mucosa," said Dr. Eduardo Franco, head of oncology at McGill University in Montreal and a world-renowned expert on the pathogen. "The oral cavity is particularly susceptible, the tissue around the tonsils and the base of the tongue."
Franco said research is increasingly pointing to "deep kissing" and oral sex as major culprits in HPV transmission. In a small proportion of those infected, mouth and throat cancers may develop years — even decades — later.
"The fact that we're seeing these things now is a reflection of ... the changes in sexual mores of the '60s and '70s, which eventually brought oral sex to be part of people's lives," he suggested.
"It takes a long time for exposure of an agent to eventually develop into cancer, so much of what began in the '60s and '70s is rolling out now in terms of an increased risk of cancer."
Those cases could be dramatically reduced — in fact, eliminated — if both girls and boys were inoculated against the most dangerous strains of HPV before they become sexually active, stressed Franco.
That's a message Terry Patterson, 52, is eager to impart after going through treatment for throat cancer that was tied to infection with HPV-16, one of the most aggressive strains of the virus.
In fall 2013, the father of four grown children had been feeling run down, his throat was persistently sore and glands in his neck were swollen. A biopsy confirmed a growth in his left tonsil was malignant.
"I was astonished," said Patterson, an insurance executive who considered himself fairly fit from recreational activities like running, cycling and playing hockey, despite being somewhat on the heavy side.
What followed was 35 days of radiation treatment — five days a week for seven weeks — at the Princess Margaret Cancer Centre in Toronto, each lasting about 45 minutes, as well as chemotherapy to prevent future recurrence of the tumour.
"It was a nightmare," Patterson said from his home in Waterloo, Ont. "It's the worst thing I've ever been through.
"My throat closed up so I couldn't eat," he said, explaining that for months all his nutrition came via a feeding tube inserted in his abdomen. "I lost 45 pounds and got third-degree burns from the radiation."
Patterson, who was recently told he is now cancer-free, encourages parents to have their children vaccinated against HPV. "I don't want anyone to go through what I did."
There are now three vaccines available in Canada that can protect against infection from up to nine different strains of HPV.
Girls aged nine and older can receive HPV inoculation through school-based programs in all provinces and territories. Six provinces — Alberta, Manitoba, Ontario, Quebec, Nova Scotia and P.E.I. — also provide HPV vaccination for boys starting at age nine.
"When most people think about HPV, they think about women and cervical cancer, but this report showed that at least one in three HPV cancers occurs in males," said Smith. "This is the first time we've had this information from Canada."
While females can have regular Pap tests to detect precancerous lesions in the cervix, there is no test for HPV-related cancers in the mouth and throat, so vaccination is the best way to prevent those diseases, said Franco, who along with the Canadian Cancer Society is urging all jurisdictions across the country to offer HPV vaccination to boys as well as girls.
Still, Franco concedes the HPV vaccine can sometimes be a hard sell.
"We're talking about a vaccine that does not have any immediate need," he said. "People don't perceive HPV as an infection like hepatitis or another infectious disease that has an immediate need of control.
"We're talking about the downstream consequences of an infection that takes 20 to 30 years to happen. So people don't perceive risk on the same basis, even though they fear cancer."
As well, Franco said the relatively small but vocal anti-vaccination movement has hurt Canadian and international public health efforts to get kids immunized — not just against HPV, but other childhood infectious diseases.
"And people don't like to talk about sex, a disease that comes from sex — and worst of all, a sexually transmitted infection that ends up causing cancer."
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News from © The Canadian Press, 2016