Causes of cancer can be placed into two rough camps: things we can control, and others that we can’t.
The latter includes things like random changes to our genes as we get older, or those that are passed down through families. By their nature, there’s not much we can do about these risks. But for the many causes we do have some control over, such as smoking, there’s a potentially life-saving chance to act.
Armed with information about what increases our risk, we can consider making changes that stack the odds of avoiding cancer in our favour. And politicians can see where action is needed most.
The goal of new data we’ve released today is to provide that information.
The data comes from a new landmark study led by Cancer Research UK researchers. It looks at the things in our lives that cause cancer and calculates how many cases in the UK are linked to each of these risk factors. We’ve done calculations like this before, but this new research uses all the latest available data and evidence to give more accurate estimates. And because some risk factors have become more common since the previous analysis, and others have become less common, it’s important to update these figures.
The findings, published in the British Journal of Cancer, show that more than 135,000 cases of cancer could be prevented in the UK each year largely through lifestyle changes – that’s around 4 in 10 cases.
And while what’s behind these cancers may not come as a surprise, the results confirm how the things we do each day can add up.
What you need to know
First, calculating these numbers isn’t about blaming someone for their cancer. This research can’t tell us what caused an individual person’s cancer – it’s almost impossible to say that for sure. It’s also important to note that this doesn’t mean that some of the remaining 6 out of 10 cancer cases can’t be prevented. It’s likely that research will uncover some other causes of cancer, or show that some known causes are linked to more types of cancer than we think, so there are some unknowns.
This research is about providing clear information on where the different causes of cancer rank against one another, to encourage people to consider making positive changes, and highlight where government can focus its efforts to prevent more cases of cancer.
“We took data from national surveys showing how common each risk factor is in the population, and data from the UK cancer registries showing how many cases of each cancer type there are. Then we searched published research for information on how much each risk factor increases cancer risk, using only gold standard epidemiology research,” says Dr Katrina Brown, who led the analysis at Cancer Research UK.
“For example, those studies compared the number of cancers in people who smoke to the number of cancers in people who are non-smokers, to get a relative risk of cancer in smokers. We used that information, along with data on how common smoking is in the UK and how many cases of smoking-related cancer types there are, to estimate how many of those cancer cases overall are due to smoking,”
The team did this for all the modifiable risk factors and found that in total, more than 135,000 cases of cancer could be prevented through changes such as:
- Stopping smoking
- Keeping a healthy weight
- Eating a healthy diet
- Enjoying the sun safely
- Avoiding certain substances at work
- Protecting against certain infections
- Cutting back on alcohol
This is also why we want the Government to make the healthy choice the easy choice. And we’re doing lots of research into other ways to prevent cancer, including studying if drugs that are already available, such as aspirin, can reduce the risk.
This latest study confirms, once again, that smoking is the biggest cause of cancer. It’s responsible for a huge 54,300 cases of cancer every year in the UK, according to our new calculations.
But the good news is that the latest data point to how prevention can be – and has been – a success.
Over recent decades, smoking rates in the UK have fallen considerably. And alongside this, we’ve also seen the proportion of cancer cases caused by smoking fall in the last five years. Fewer people smoking means fewer cancer cases caused by smoking.
But the results also underscore how we can’t be complacent when it comes to tobacco.
“Even though smoking prevalence is falling in the population, smoking has a massive impact on the cancer risk of people who do it, therefore it’s still generating a huge number of cancer cases,” says Brown.
The number of UK smokers has fallen, and we hope that will continue, so the proportion of cancers caused by smoking will continue to follow that trend too.
This success also highlights how changes at the population level could reduce the impact of other cancer risk factors too. And obesity is an important example of this.
Obesity causes more than 60 cases of cancer a day
Being overweight or obese increases the risk of 13 different types of cancer, and causes around 22,800 cases of cancer in the UK every year, according to the new data. That makes it the second biggest cause of cancer in the UK after smoking.
But only 15% of people know that obesity causes cancer. So this is an important issue to raise, which is the aim of our much-discussed national awareness campaign. Unlike smoking rates, obesity levels have overall risen over the last couple of decades. And if we don’t act, the number of cancer cases caused by obesity will follow this trend too.
What does this mean for me?
It’s important to say again that this research can’t tell what has caused or will cause an individual’s cancer. The data come from comparing large groups of people. So, while research has shown that, for example, being overweight can increase the risk of cancer, it doesn’t mean you will definitely get cancer if you are overweight. And this is true for the other risk factors as well.
“This research was looking at the impact of these risk factors on a population level, rather than the effect they would have for an individual person,” says Brown. “But it can give us an indication of the relative importance of the risk factors for individuals. This is because it considers how much the factor increases individual risk, how many cancer types are affected, and whether those are common cancer types.”
Read more: 10 health hacks to help cut cancer risk
Adding up the number of UK cancer cases caused by these risk factors confirms that around 4 in 10 are preventable. This shows there are steps we can all take to reduce our risk of cancer.
Prevention is not a promise. We can’t say for sure that not smoking, keeping a healthy weight or avoiding alcohol will mean you won’t get cancer, but it could help stack the odds in your favour.
To help pick out where you might start, we’ve built an interactive health checker that can help you understand what raises your risk and what you can do to reduce it.
Give it a go: What’s my cancer risk?
Sophia Lowes is a health information officer at Cancer Research UK
Find out more about all the causes of cancer included in the analysis on our website.
Brown, et al. (2018) The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. BJC. 10.1038/s41416-018-0029-6DOI: