Mouth cancer rates are increasing, but why?

Over the decades, our society has changed enormously – and with it our lifestyles.

And because the rates of many types of cancer are linked to things we do (or not) every day, as well as our jobs and things in our environment, cancer rates have changed too.

November is mouth cancer action month. Mouth cancers are now the tenth most common cancer in UK men, and fifteenth most common in UK women.

That’s compared to thirteenth in men, and seventeenth in women, back in 2002.

To put this in context, the rate of being diagnosed has risen by around a third over that period, increasing from nine cases per 100,000 people in 2002 to 12 cases per 100,000 in 2012.

These may seem like worrying statistics, so what can be done to halt the rise?

In fact, nine in 10 (91 per cent) oral cancer cases could potentially be prevented. The disease is more common among people who smoke, have a diet low in fruit and vegetables, or drink alcohol. And some cases are linked to infection with the human papillomavirus (HPV) – which is often talked about in relation to cervical cancer.

So which of these is to blame for the rising rates? As you’ll find out below, it’s a pretty complex picture. But first, some background.

What are oral cancers?

The term ‘oral cancer’ actually covers a number of different cancers. But the majority – around four in five cases – are cancers of the tongue, the inside of the mouth, tonsils, and the middle part of the throat (oropharynx).

And it’s changes to how many of these cancer types are being diagnosed that account for the overall increase in rates over the past decade.

In fact, the rate of people being diagnosed with tongue, tonsil and oropharyngeal cancers has increased by almost 60 per cent in the last 10 years.

Overall the rates of tongue, tonsil and oropharyngeal cancers together have risen from four in every 100,000 people ten years ago to around six in every 100,000 today.

Or in terms of cases, that’s an increase from around 2,100 to 3,700 people a year in the UK.

So what’s to blame for these rising rates?

Why the increase?

Evidence suggests that tobacco, not eating enough fruit and vegetables, and drinking alcohol all increase the risk of oral cancer.

In fact, smoking is linked to around two thirds of oral cancer cases, and not eating enough fruit and veg is linked to more than half. And alcohol is linked to just less than a third.

If you’re mathematically inclined, you’ll notice that two thirds, plus a half, plus a third is more than all cases of oral cancer.

That’s because, for many cases, there’s more than one factor involved. For example, people who smoke might also drink alcohol regularly. And people who drink regularly, might not always eat five-a-day, every day. The studies used to make these calculations did take into account that people might do more than one of these things – but if we look at the risk factors separately, they make up the fractions above.

So what’s been happening to these risk factors over time?

First, the good news: the rate of smoking has decreased overall in Great Britain in the past 40 years or so.

But this doesn’t mean that the number of smoking-related cancers is also decreasing.

If we look at lung cancer data, yes – the rate of lung cancer in men is falling following the decline in smoking rates. But the rate of lung cancer in women is increasing. This is due to the rise in smoking rates in women in the 1950s and 60s, which could also be contributing to the increase in oral cancer rates. We do expect to see a decline in lung cancer rates in women though, much like we have seen in men.

Is it the same for alcohol?

The Office for National Statistics recently reported a decline in adult drinkers in Great Britain. But this decline only started in 2005.

Public Health England blogged about these data and used statistics from the British Beer and Pub Association to show that if we step back further in time, the trends look a lot worse. So what do we see?

Again, there was an increase in the average amount of alcohol people drank in the UK.

The amount the UK drinks has nearly doubled since the 1960s. This is likely to result in an increase in oral cancers later on.

For fruit and veg consumption it’s a bit more complicated. The Health Survey for England recently published data showing that only a quarter of men, just over a quarter of women (28 per cent), and 16 per cent of children in England are getting their five-a-day.

This seems pretty low.

The data also tell us that the percentages peaked in 2006 and have since fallen. This makes it difficult to draw any conclusions about the trends in fruit and veg consumption and whether it has affected oral cancer rates.

But there’s also another cause of oral cancers, for which evidence has been growing in recent years: the human papillomavirus (HPV) – more commonly linked to cervical cancer.

What about HPV?

A few years ago we blogged about the link between HPV infection and oral cancer – particularly how oral sex might play a role in transmitting the virus, and what we do and don’t know and since then the picture hasn’t become much clearer.

Up to eight out of 10 people will be infected with HPV at some point in their lives. So the infection is extremely common, but although there are over a hundred types of HPV, only thirteen are linked to cancer.  In many cases the body’s natural defences will fight off the infection without the person ever knowing.

But in some cases the infection persists, triggering a series of events that can lead to cancer. Researchers are trying to pin down exactly what these events are, and use this information to tackle these cancers.

Either way, the evidence suggests that about seven in every hundred oral cancers in the UK are linked to HPV – that’s far fewer than are caused by smoking, drinking alcohol or not eating your five-a-day.

So how have our behaviours changed over time?

Sexual behaviours can be hard to study, partly because of taboos around talking about them. But, this report in The Lancet on sexual attitudes and behaviours showed an increase in the percentage of people in Britain practising oral sex with someone of the opposite sex between the early and late 90s, increasing from 70 to 78 per cent in men and from 66 to 77 per cent in women.

This could explain part of the increase we’ve seen in oral cancer rates, but we don’t know enough about how long it takes for an HPV infection to lead to oral cancer, or how often it actually does.

It also seems unlikely that the full increase in oral cancer rates is just down to more people having oral sex – considering the percentage of cases HPV is linked to, and the evidence we’ve seen for the other risk factors.

So we’re not suggesting you become celibate. And we’re certainly not saying that an oral infection with HPV will definitely lead to oral cancer.

Instead, we’re highlighting these issues as part of our work helping doctors and dentists spot the symptoms of oral cancer – from any cause – to try and boost the number of oral cancers diagnosed at an earlier stage.

What are we doing?

We’ve been working with the British Dental Association and the Royal College of General Practitioners on a toolkit that contains simple information packs and videos – much like the skin cancer one we made with the British Association of Dermatologists a few years ago – that will be open to all GPs and dental health professionals to help them spot the signs of oral cancer early.

We hope this will improve their confidence in spotting the signs of oral cancer and referring people who have suspected oral cancer for further tests.

What next?

We’ve mentioned why we’re helping doctors and dentists spot the signs as early as possible.

But the fact that so many cases are linked to our lifestyles serves as a reminder that beating cancer isn’t just about cures and treatments – we need action on prevention too.

We’re campaigning for action against tobacco, and trying to help people quit smoking, cut down on alcohol and get plenty of fruit and veg into their diet. We’d also like to see the HPV vaccination programme being extended to include boys as well as girls, which is being considered at the moment by the Joint Committee on Vaccination and Immunisation – we hope that they and the Department of Health can find a way to do this affordably.

In the last 10 years we’ve seen rates of oral cancers increasing. So now, knowing what we know, can we see oral cancer rates dropping in the future?

With sustained action – from doctors and dentists in spotting it early, policy makers in helping create a healthier society, and changes we can make to live healthier lives – we have high hopes that we can.

Harriet Rumgay is a cancer information analyst at Cancer Research UK

Graphics by Liz Gould, information designer at Cancer Research UK

Statistics used were calculated by the Statistical Information Team at Cancer Research UK.

Find out more:

• Read about the signs and symptoms of oral cancer
• Find out more about how to reduce your risk of cancer