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You’ll probably have seen the media coverage today about aspirin, and whether it can help prevent cancer.

The news comes from a new scientific report by international experts (including some funded by Cancer Research UK), looking at all the available evidence about the over-the-counter drug’s pros and cons.

So what are they saying? And should you or I start taking it today? Well, the drug has risks as well as benefits, so our advice is: don’t take it without talking to your GP.

This graphic sums up the new data, and the unanswered questions:

Aspirin infographic

So why the uncertainty?

The story so far

Today’s headlines are the latest chapter in a story that’s been unfolding over the last few years. We’ve been following it since 2008, when we wrote this in-depth explainer about the state of the evidence.

In 2009, our researchers produced a new report, discussed here, concluding that more research was still needed.

Then, in 2010, a new analysis by researchers in Oxford suggested that the pros were beginning to outweigh the cons – although our experts still called for caution.

The last big announcement on the subject came in 2012, when the Oxford team published new data refining what was known about the balance of pros and cons. We discussed this extensively and, if you read one post on the subject, it’s this one, as it goes into detail about how the risks and benefits change over time.

So what’s new?

Ongoing studies

We’re funding several studies looking at aspirin in more detail, including:

  • CAPP3, to look at the best dose of aspirin to prevent  bowel cancer in people at high risk of the disease
  • AspECT, to look at whether it can prevent oesophageal cancer in patients with Barrett’s oesophagus, a condition that increases risk.
  • Add-Aspirin to look at whether aspirin can enhance the benefits of treatment in people already diagnosed with cancer.

And so to today’s news. The latest analysis, published in the Annals of Oncology, pulls together data from all available studies and clinical trials, and analyses where the balance lies more clearly than ever before.

It confirms that aspirin protects most strongly against bowel, stomach and oesophageal cancers, and also more weakly against lung, prostate and breast cancers.

It suggests that the benefits start building from age 50, so there’s little to gain from taking it below that age.

And it finds that if 1,000 people (500 men and 500 women) aged 60 take aspirin for ten years then – compared with 1,000 people who DIDN’T take aspirin – over the next 20 years you’d see:


Around 17 fewer deaths, including:

  • 16 fewer deaths from cancer overall
  • 1.4 fewer deaths from heart attacks


Between two and three extra death from:

  • 1.4 more lethal strokes
  • 0.3 more serious peptic ulcers
  • 0.65 more lethal gastric bleeds

Sounds positive overall, right? Well there are a few important omissions from the analysis that begin to muddy the waters.

It’s a bit more complicated than that

These risks and benefits aren’t evenly spread around the population. Some are at higher risk of side effects. Some people’s genetic make-up means they break down aspirin at different rates – some faster, some slower, than average. Some will have a lower risk of cancer without even taking the drug, so they won’t benefit as much (though they may still experience side effects). It’s an extremely complex, and still slightly murky,  picture.

So to be able to recommend aspirin to people in the full knowledge that the risks are being minimised, and the benefits maximised, doctors need to have a better idea of the following:

  • What age should people start, and stop, taking aspirin?
  • What dose should they take?
  • What are the factors that should rule someone out from taking aspirin, and how should we test for them?

At the moment, frustratingly, there’s no clear, definitive answer to these questions. And until there are, we’re discouraging people from stocking up on their own supplies of aspirin without seeking medical advice first.

So if you’re worried about your risk of cancer, and want to do something about it, your first port of call should always be your GP.




Patricia Byrne September 4, 2014

Well done very clear and helpful article

Alanah Wilson September 4, 2014

I think its certainly something to be further investigated, this has happened before , that a drug that has been given to treat one ailment , has been found to benefit people with other medical problems.

Susan Haslam September 4, 2014

I feel that it is a gamble to start taking aspirin to try to prevent cancer at the moment as the studies are not at all conclusive yet. Also people may think because they are taking aspirin they need not look after their health so much ie. not being careful with their diet, not smoking and not doing enough exercise etc.

Ruth Plom September 4, 2014

Some Asthmatics – including me – are allergic to aspirin, and it can cause an asthma attack. I think this should be mentioned in your articles.

mel September 4, 2014

Don’t take it unless necessary had family members as well as myself they are no longer here and I suffered a bleed that nearly cost me my life!

Eileen Frost September 4, 2014

Interesting! I’ve been on a dose of one 75gm aspirin a day since I had a stroke about 15 years ago, and am quite thankful, because as I am overweight (have struggled with my weight for years, although I do eat carefully now) I understand, rightly or wrongly, that overweight can in some circumstances, lead to cancer. At the time of the stroke my cholesterol was 9.5! but due to simvastatin 40gm daily dose and the aspirin to keep my blood thinner, I’m still alive at the age of 71. My cholesterol usually runs around 2-3 nowadays, and I have much to be thankful for. Maybe the aspirin is helping me? I do appreciate your emails to me and keep up the good work. The sooner we can eradicate this disease the better. Thank you.

Joanna Holding September 4, 2014

very interesting. I have been taking 75mg aspirin dailing since I first heard that it was thought to protect against cancer. My mother had 2 mastectomies for breast cancer but survived and lived to 90 but one of my sisters died after 12 yrs fighting the disease.

Kevin webb September 4, 2014

Very interesting. I know from experience that Aspirin (Salicylic acid) can help protec against heart attacks; but this is a new one on me. I hear similar claims for chewing raw cloves of garlic – but again, not sure. The main difference is that the garlic is natural; and aspirin derives from the bark of silver birch trees (No one is suggesting chewing this). Could be. But we need a lot more information and cerdible data.

kevin martin September 4, 2014

I would always use caution with Aspirin due to the side effects, I use Fruitflow as a natural alturnitive.

Colin September 4, 2014

“At the moment, frustratingly, there’s no clear, definitive answer to these questions. And until there are, we’re discouraging people from stocking up on their own supplies of aspirin without seeking medical advice first.
So if you’re worried about your risk of cancer, and want to do something about it, your first port of call should always be your GP.”
So, given the unknowns, what could a GP advise? Better to make your own mind up and hope for the best!

Garry September 4, 2014

I am 52 and having watched my Mother die from rapid cervical cancer in 2009 I have been taking 75mg asprin daily since. I believe if you can get past 3 yrs with no ill effects you should be fine. Not only that they are dirt cheap so its not much of a risk to take.

S Rapaport September 4, 2014

Nice article, well-written, and with the real numbers properly explained. But I’m not enthusiastic about the ‘consult your GP’ conclusion. In my experience, GPs vary tremendously on their level of updates regarding new science.

Even a very well-informed GP won’t really know more about this result than someone who read this article and the Medscape article from last month that it refers to. So the only benefit of their advice will be their knowledge of your individual genetic conditions and blood chemistry, and how they interact with the study.

Now, how many people here under 60 can say ‘My GP is intimately familiar with my blood chemistry and genetic peculiarities’? Didn’t think so. But even if you could, the interactions between those and the study’s conclusions isn’t even known yet, so your GP won’t know that answer either. He or she will just offer an opinion based on their own experiences and prejudices.

I’d change the ending to ‘take your chances or wait for further research’, and leave the poor GPs out of it.

R Masters September 4, 2014

Very good info

Mohammed A Haque September 4, 2014

Encouraging report

Gary Slater September 4, 2014

Expert opinion: aspirin and cancer – the unanswered questions
Category: Science Blog December 7, 2010
In the light of today’s headlines about aspirin and cancer, we spoke to one of our leading scientists Professor Janusz Jankowski, who’s running a clinical trial – AspECT – looking at whether aspirin can prevent oesophageal and bowel cancer. Here are his opinions and concerns about the latest findings:

Aspirin’s ability to prevent cancer, especially cancers of the digestive system (oesophagus, stomach and bowel cancers) is well known.

But before we can recommend that people take aspirin, there are several important things to learn about whether long-term low-dose aspirin use is beneficial overall.

How common are side-effects?

Aspirin has several serious side effects. Most importantly, aspirin can increase the chances of developing stomach ulcers – which can cause bleeding. In people over 75, this can be fatal. The true frequency of aspirin-related stomach ulcers varies depending on the method used to measure it – it can be anywhere from 0.1 to 2 per cent of people taking aspirin, every year. However, drugs called ‘proton pump inhibitors’ can reduce the likelihood of bleeding from stomach ulcers caused by aspirin by up to fifty per cent.

Aspirin has other side-effects. In very rare cases, it can increase the chances of bleeding in the brain. About one in a hundred people taking aspirin have an allergic reaction. And about one in ten find it can make their asthma worse.

Who will benefit?

Secondly, because we’re all genetically different, and have different lifestyles, aspirin probably doesn’t prevent cancer in everyone who takes it. A reasonable estimate, based on the available research, is that about a quarter (25 per cent) of people will benefit – but this figure may be as low as a fifth (20 per cent). So the majority of people taking aspirin may not in fact benefit from it.

This ‘aspirin resistance’ seems to be widespread, and we don’t yet know what causes it. So we don’t know who should take aspirin. To clarify this, we need large genetic studies to discover who will benefit from low-dose aspirin.

What dose?

Thirdly, we don’t know what dose of aspirin is best. While the current paper has looked at 75mg of aspirin we don’t know that 150 or even 300mg isn’t better. This is vital – the commonest reason drugs don’t work is the dose is wrong.

A premature rush to using aspirin in too small a dose in the population could result in many people being deprived of benefit.

How long should you take it for?

Fourth, we don’t know how long a person has to take aspirin to get a protective effect.

The current paper indicates an unusually rapid response for this: five years. This is unique and in many ways doesn’t fit with how we understand cancer develops.

In particular, in order to stop cancer developing we believe aspirin must be taken at a very early stage in cancer’s development, before it becomes ‘full-blown’ cancer. This prevents the small groups of abnormal cells obtaining more genetic changes that will eventually become cancer. We believe this takes about 10 to 15 years.

What has been done by Cancer Research UK in this area?

The trial I work on – AspECT – was specifically designed to measure rates of oesophageal cancer, bowel cancer and deaths from heart disease.

The trial is split into four groups:

people only given a low-dose proton pump inhibitor
people only given a high-dose proton pump inhibitor
people given a low-dose proton pump inhibitor with 300mg aspirin
people given a high-dose proton pump inhibitor with 300mg aspirin
To date, the team behind the trial haven’t revealed any obvious differences between these four groups. .

While we strongly endorse this recent study, much caution is needed. The study looked at trials that focused on heart disease rather than cancer, and that might have biased the results.

For example, the number of deaths from cancer of the digestive system was just 182 out of almost 20,000 patients. There were only 23 deaths from oesophageal cancer. That’s a very small number to be trying to draw firm conclusions from.

Patients on these trials, especially those who were taking aspirin, might also have had medical complications that resulted in them being diagnosed at an earlier stage (when cancers are easier to treat successfully).

In short, before making any broad recommendations, we need trials like AspECT to report their findings. AspECT’s preliminary data will be available in 2012. These will cover issues of risk benefit, genetic stratification for response, dose and length of therapy, and should go a long way towards answering these crucial questions

Dave Corbett September 4, 2014

What really needs to be understood is the mechanism by which aspirin can be having such varied effects – are they real, or as the article discusses are a complicated combination of other factors making it look like aspirin is doing this

Jane Oldfield September 4, 2014

Having survived colon cancer aged just 46 in 1997 I would love to believe I could cut my risk of it reoccuring but I cannot tolerate any anti-inflamatory painkillers so it’s not an option for me. I was not overweight and did not consume a lot of processed meats so the doctors thought I was low risk. Since then I’ve lost my younger brother and a cousin (just 43 when he died) so unless we are just unlucky I believe there’s a genetic factor involved so how can there be any help for that?

Mrs. M. Cartmell September 4, 2014

My mother decided to take half an aspirin every day thirty years ago with no doctor’s advice. Although very frail now at 96 she still plays a good game of bridge and has just about got the hang of her ipad.

CJC September 4, 2014

My husband had bowel cancer three years ago and has been taking 75mg Aspirin every day since. He did speak to his GP who more or less told him to take it if he felt it would help. Not helpful advice. All scans have been clear since.

Hugh Avonalaff September 4, 2014

I guarantee my GP would Google the internet before he advised me what to do.

VERITY September 4, 2014

A few years ago it was reported in the press that taking a low dose aspirin daily could help prevent bowel cancer. We started breaking the standard dose aspirin into quarters and taking one quarter a day which seemed like quite a good idea. May start doing this again in light of recent reports. Can’t imagine my GP will have much of an opinion on it-don’t have very much faith in GP’s being experienced in this at the moment. . . but interested to learn of other’s experience of asking their GP’s?

Allan del Fonso August 7, 2014

i’ve been taking aspirin everyday for the last five years

celia August 6, 2014

taking a small aspirin daily is better than being poisoned by chemo