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.
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.
Rothwell, P., Fowkes, F., Belch, J., Ogawa, H., Warlow, C., & Meade, T. (2010). Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials The Lancet DOI: 10.1016/S0140-6736(10)62110-1
Brian Shrimplin February 7, 2011
Just a quick point on Jim’s comment, as I understand it, Aspirin does not actually ‘Thin’ the blood, it makes it less glutinous or ‘sticky’. This helps to prevent it building and blocking up small Arterial walls Etc.
Jim Sumner February 4, 2011
About 20 years ago I was advised to take 75mg of soluble asprin per day to keep my blood thin. This I have done. I am 80 and I have had no ill effects so far. Each time new research advises asprin to prevent this and that I feel quite pleased as I’m already taking it. I have no other medication so hey, here’s to the next 20 years.
Karen Barnes February 4, 2011
Unfortunately due to a problem with clotting my sons and myself cannot take aspirin or quinine, does this mean our chances of getting cancer are higher than everyone elses?
David Harbour February 4, 2011
I have been taking .75 of Asprin for appx 14 years but it did not prevent me from getting prostrate cancer. Fortunately I have just gone into remission from this.
A. Basu February 4, 2011
Since my stroke in 1998, I have been taking under prescription Asasntin Retard capsule each twice a day. I believe there is small element of aspirin in it. Am I in any danger? For my inflamation etc. I take paracetamol.
Erwin February 4, 2011
I was taking a 75mg dose of Aspirin daily up until 2007. In April 2008 I was diagnosed with rectal cancer and in September 2008 I had a radical peroneal resection with permanent colostomy. Now I am wondering from this article if indeed the aspirin worked against me.
Margaret Bell February 3, 2011
I can’t beleieve “only 23 People died from Oesophagus cancer” My husband recently died only 8 weeks after being diagnosed with this cancer. It is common knowledge that by the time this cancer is diagnosed it is too far advanced for any treatment whatsoever. So explain please how aspirin could be prescribed to help this?
Mark February 3, 2011
To adam… What is meant is 25 percent of the population would benefit from taking aspirin, but not all cancer sufferers might be in that 25 percent bracket, for example half of cancer patients could be in the 75 percent bracket where aspirin has no effect. I believe this is what the proffesor was getting at.
Adam December 8, 2010
Ed, that would only make sense if the incidence of cancer went down to zero in people who take aspirin. Approx 25% of people die of cancer, so saying that 25% of people who take aspirin would benefit is equivalent to cancer being wiped out entirely.
That can’t be right, and some stats must have got muddled up somewhere.
Ed Yong December 8, 2010
Adam, he meant “a quarter of people *taking aspirin* would benefit from it”.
Steve Johnson December 7, 2010
My father takes half an asprin everyday after his triple bypass but I thought that you have to be very careful as it can have some adverse affects.
so I beleive it is on doctors orders only!
Ruth Seeley December 7, 2010
As someone whose father was given aspirin during a cerebral hemorrhage (he’d also been told to take aspirin for arthritis in such massive doses it had caused a stomach ulcer), AND as someone who does media relations, these headlines are extremely perturbing. You don’t mention the other major contra-indication, which is people already taking blood thinners for, say, congestive heart failure. My concern is the fact that it’s an over-the-counter medication, and that we still live in a world where people are convinced if one is good, 20 are better – and a world in which some people still don’t understand and won’t follow prescription medication instructions and ‘save’ a few of their antibiotics for the next time they get a cold.
Still, thank you for raising many of the concerns we should all share before getting onto the ‘a dose of ASA a day will make you immortal’ bandwagon.
Adam December 7, 2010
Interesting post, and similar in many ways to my own thoughts. Totally agree that we still have much to learn about aspirin.
However, one of your stats looked a bit odd. You said that about a quarter of people will benefit. Since only about a quarter of people die of cancer anyway, that would imply that aspirin has 100% efficacy in preventing cancer. Did you mean to write that?