Watch: Global News reporter Carey Marsden looks into the increasing rates of throat cancer related to HPV.
TORONTO – The good news: Fewer Canadians are getting throat cancer from heavy drinking or smoking.
The bad news: More Canadians are getting throat cancers related to the human papillomavirus (HPV).
The worse news: The more oral sex you have and the more people you have it with, the higher your risk of contracting the virus.
Younger, healthier cancer patients means higher survival rates, but gives oncologists a different challenge: making treatment bearable for cancer survivors with decades to live.
Scientists from London, Ont.’s Lawson Health Research Institute studied tonsil cancer tumour samples over almost two decades and found there are more cases of tonsil cancer, and more cases caused by HPV.
Rates of sexually transmitted infections have been steadily increasing because of changes in sexual practices, the authors note – in this case, a rise in number of oral sex partners, and particularly for men. Author David Palma says for every woman who gets HPV-related throat cancer, three men will contract the disease.
The link between HPV and oral cancer made headlines in early June, when actor Michael Douglas reportedly attributed his illness to oral sex (though his spokesman later said Douglas was only discussing what causes oral cancer during the interview, and never that it was the cause of his cancer).
Read more: Michael Douglas’ throat cancer throws spotlight on HPV and oral cancer
“We know from studies in the 1970s and 1980s that there have been changes in sexual practices that generally included a change toward more oral sex,” Palma said. “What that has made people at risk for is getting HPV infection…And our study is the first to really show—by looking at the DNA within the tumours themselves—that we’re seeing a rise in these HPV-related throat cancers.”
Read more: Cervical cancer virus fuelling rise in oral cancer: study
The paper, published in the latest edition of the Current Oncology journal, analyzed DNA from 160 tonsil cancer patients’ tumours at the London Health Sciences Centre between 1993 and 2011. Time periods were then broken down into 1993-1999, 2000-2005 and 2006-2011.
The study found a significant increase in the total number of tonsil cancers between the first two time periods: from 32 in 1993–1999 to 68 in 2006–2011. The number of HPV-positive cases also increased from 25 per cent to 62 per cent. Those were associated with a 45 per cent improvement in five-year overall survival.
Palma says these cancers caused by HPV affect people who are younger and healthier; 20 years ago, throat cancer was more common for smokers or drinkers in their 70s.
“Because of the good work that’s been done with reducing smoking, we’re seeing fewer and fewer of these smoking-related cancers,” he said. “But then about 10 years ago, people began to notice non-smokers were coming in with throat cancers. And these non-smokers were healthy: 40, 50, 60 years old.”
The study author notes that 80 per cent of sexually active young adults will be exposed to the virus at some point in their life. For most people, it clears up on its own.
“In a small percentage of people, the virus integrates itself into the cells in the back of the throat, and stays there for many years. Then 20 years later, it causes cancer,” he said, adding that really healthy people who develop cancer and haven’t engaged in traditionally “risky” things like smoking and drinking tend to be surprised.
Palma adds that the risk for these cancers increases as people have more oral sex or more sex partners. But many of his patients have only had one or two sexual partners in their lifetime.
“We’re obviously not calling for a ban on oral sex, but I think it’s important for people to realize that these behaviours can be potentially risky.”
One preventative measure is the HPV vaccine offered to Canadian girls starting as young as Grade 4 (depending on their province). The vaccine targets a strain called HPV-16, which causes 95 per cent of throat cancers, according to Palma. He adds that the chances of seeing an HPV infection in the saliva of those who’ve received the vaccine goes down by about 93 per cent, but only time will tell if it prevents throat cancers.
“We won’t know for sure until enough time goes by that we see the rates of cancers come down – so about 20 years,” he said. “Until the people who’ve been vaccinated don’t develop these cancers.”
Kevin Higgins, head and neck surgical oncologist at the Odette Cancer Centre in Sunnybrook Hospital, says the findings of the London study echo what he sees at his cancer centre with a changing demographic in throat cancer. He also believes the vaccine is a good option, and that widespread availability for young men as well as young women is the best strategy.
Dr. Robert Nuttall, acting director of the Canadian Cancer Society, adds that oropharyngeal cancer is a relatively rare cancer in Canada, but that HPV is a cause of several cancers.
“We know the HPV vaccine can prevent cancers of the cervix, vulva, vagina and anus and this study suggests that the vaccine may also prevent some cancers of the throat,” wrote Nuttall in a statement to Global News.
Palma says what’s most needed is more research to determine how best to treat cases of throat cancer – especially in a younger population of patients who may have to live with side effects of current treatment for a long time.
While he says these HPV-related cancers are highly curable (at 80 or 90 per cent of patients), it’s usually with chemotherapy and radiation, which can cause difficulty swallowing or, in some cases, dependence on a feeding tube.
“So we need to determine how to best treat these cases: Can we dial back the radiation, or can we dial back the chemotherapy, or maybe use new surgeries?” he suggested. “So we need more research in this area.”
Note: The London study was funded by a research grant from Merck Canada Inc., maker of the HPV vaccine Gardasil. In the paper, the authors declared that no financial conflict of interest exists.
With files from Carey Marsden
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