HPV’s deadly oral cancer connection

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HPV infection has become firmly established as an aetiologic risk factor for cancers of the oropharynx, specifically those of the tonsils and the base of the tongue.
HPV infection has become firmly established as an aetiologic risk factor for cancers of the oropharynx, specifically those of the tonsils and the base of the tongue.

Academics have recently discovered the link between HPV and oral cancers. It is a health problem that is on the rise, and dentists have a vital role to play in its treatment. Chris Sheedy reports

Professor Ian Frazer was a relatively unknown academic until 2006, when suddenly it seemed the eyes of the entire world were turned upon him. That year he was made the Queenslander of the Year and the Australian of the Year. In 2007, he was awarded the Florey Medal for medical research and in 2008, the Prime Minister’s Prize for Science. Since then, the pattern has continued but what had he done to achieve such acclaim?

Prof Frazer and his colleagues had been central to the development of the human papillomavirus (HPV) vaccine, now marketed as Gardasil or Cervarix, that immunises against cervical cancer—the first vaccine specifically designed to prevent a cancer.

As if that development wasn’t enough, the scientific world soon realised that the vaccine would likely also protect against several other types of cancers previously considered unrelated to HPV.

In April this year, the American Dental Association released a statement on HPV and squamous cell cancers of the oropharynx. It reported what the scientific world had been gradually realising over the past five to 10 years that “HPV infection has become firmly established as an aetiologic risk factor for cancers of the oropharynx, specifically those of the tonsils and the base of the tongue”.

In the past, it had been considered that oral cancers mainly affected older men who smoked and drank. But as the number of smokers reduced and those particular types of front-of-mouth oral cancers declined, we saw an increase in HPV-related oropharyngeal cancers. The American Dental Association put the increase, from 1988 to 2004, at 225 per cent. So, Prof Frazer’s vaccine, and Australia’s world-leading vaccination program, is now also targeting boys. It is seen as a powerful weapon in the war against oral cancers. But what is the reason for the growth in these cancers? And what role should dentists play?

“There are two groups of oral cancers,” explains Basil Donovan, Professor of Sexual Health at the University of New South Wales’s Kirby Institute. “One group is broadly referred to as ‘toxin related cancers’. They are predominantly related to smoking and, to a lesser extent, alcohol. They tend to be in the front half of the mouth and have a much poorer prognosis. The HPV-related cancers tend to be in the back half of the oropharynx, particularly the tonsils, and they have a much better prognosis and survival rate. The dominant virus in oropharyngeal cancers is HPV 16. We think it took off with the growth in popularity of oral sex. It will increase over the next generation but thereafter, the vaccinated cohort will start coming through. Our national immunisation program sees the vaccine given routinely to girls and boys around the ages of 12 or 13. Girls began in 2007 and boys in 2013.”

Girls began before boys, Prof Donovan says, because the primary condition the vaccine was preventing was cancer of the cervix. But since the program was launched, it became apparent that cancers of the cervix make up only 50 per cent of HPV-related cancers.

“So, the preventative effects of the vaccine for oropharyngeal cancers, in males as well as females, is a fringe benefit,” Prof Donovan says. “It was not one of the aims of the original vaccine program.”

In the decades until the population-wide effects of the vaccine are felt, there is plenty dentists should be doing in order to play their role in the continuum of care. However, how does a dentist, during a regular check-up, introduce the topic of oral sex?

“Are dentists comfortable talking about this to patients?” asks Dr Peter Alldritt, chair of the Oral Health Committee at the Australian Dental Association. “Actually, dentists have been faced with a similar challenge before. It took dentists a long time to work out how to start encouraging people to stop smoking. A lot of dentists initially said they didn’t feel it was their job, or they didn’t feel comfortable, to do that. With HPV-related cancers, I think the profession is now facing that hurdle again, this time in talking to patients about the possibility of transmitting HPV through oral sex.”

Dr Alldritt says he approaches the topic in a general manner. As he looks in the mouth and under the tongue, he tells the patient what he’s looking for—lumps, bumps, red patches and ulcers. He then explains, as he does so, that smoking, heavy alcohol consumption and even oral sex are risk factors for oral cancer.

So, you are just putting it out there as a general comment,” he says. “You’re not asking any personal questions. You’re not asking the patient whether oral sex is a risk factor for them. But if you speak in general terms about what the risk factors are then sometimes an alarm will sound for that patient.”

In terms of physical examinations, Dr Alldritt says a dentist should begin on the outside of the face and neck. “We should be looking at our patients’ faces first of all, looking for lumps and bumps that appear in the neck and the jawline. These can be warning signs,” he says.

“Dentists should not be afraid to put their hands on somebody’s jaw and feel under the jaw and around the neck, feeling for enlarged lymph nodes which can be a sign of oral cancer.

“When we look in the mouth, we should not just be looking at teeth and gums. We should also be looking under the tongue and at the roof of the mouth and on the palate. We should look down the throat a little. After all, if we’re not looking inside this person’s mouth for specific warning signs, who else is going to do it?”

Currently in Australia, six people are diagnosed every day with oral cancers and one person dies every day from oral cancer. By examining patients, informing them of risks and referring them onwards when necessary to an ear-nose-throat surgeon, dentists can save lives. ≤

For more on this topic, and a patient-friendly handout, download the ADA’s The Young Person’s Oral Survival Guide: www.dentalhealthweek.com.au/2013/downloads/survival_guide_web.pdf

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