Find out about the research into aspirin and cancer, what you need to know and what researchers still need to find out.
Should I take aspirin?
There is some evidence showing that aspirin may help to prevent some cancers and lower the risk of it spreading. But this doesn't mean that everyone, particularly people with cancer, should start taking aspirin.
There are no national guidelines recommending people to take aspirin in the UK to prevent cancer, or stop cancer spreading. There are still many questions we need to answer.
Also, aspirin can cause serious side effects for some people, such as internal bleeding. Some people with cancer already have a higher than normal risk of bleeding, because of their cancer or treatment.
Some cancer drugs can also cause significant side effects when taken with aspirin. Aspirin can cause serious complications in people with other medical conditions such as:
- stomach ulcers
- haemophilia – a type of blood clotting disorder
The dose of aspirin
In trials so far, the amounts of aspirin taken each day varied from 75mg to 300mg. That’s between a junior aspirin (75mg) and one regular aspirin (300mg).
We don’t know exactly how much aspirin people need to take, if it can help to prevent cancer or stop it spreading. As with any drug, it’s important not to take too much because you could increase your risk of serious side effects.
What research shows about aspirin and cancer
The research done so far shows that aspirin might lower the risk of dying from cancer. And it might lower the risk of some cancers spreading to other parts of the body. But because aspirin can also cause serious side effects for some people, we don’t know whether the benefits of taking it always outweigh the risks.
2012 research study
A research study in 2012 looked at 5 trials which had been testing whether aspirin could prevent major heart and blood circulation problems in healthy people.
People taking part in these trials were put into 2 groups. One group took aspirin every day and the other group had no treatment.
The researchers then looked at all the people in the two groups who went on to develop cancer. They compared:
- the types of cancer diagnosed
- how many people who developed cancer went on to have a spread of that cancer (secondary cancer)
- how many people already had cancer that had spread when they were diagnosed
The researchers found that in people who were diagnosed with an early stage (localised) cancer, those who took aspirin were less likely to develop a secondary cancer later on. So taking aspirin seemed to lower the risk of the cancer spreading.
The researchers also found that people taking aspirin were less likely to have a cancer that had spread when they were first diagnosed. A third fewer people who took aspirin had a spread of their cancer at diagnosis.
Another finding was that the greatest benefit was for a type of cancer called adenocarcinoma. This includes many common cancers, such as breast and bowel cancers. In people taking aspirin who had adenocarcinoma, 70% fewer developed a secondary cancer than the researchers would have expected.
In August 2014 scientists published an analysis of previous aspirin studies. The study confirmed that aspirin can lower the risk of developing bowel, stomach and oesophageal cancers.
It can also lower the risk of lung, prostate and breast cancers but not as much as the other cancer types.
Cancer Research UK is helping to fund the world's largest clinical trial looking at aspirin to stop cancer coming back.
The ADD-Aspirin trial wants to find out if taking aspirin every day for 5 years can stop or delay an early cancer from returning. 11,000 people who have had, or are having, treatment for cancer will take part. The trial is for people with cancer of the:
- oesophagus (food pipe)
The trial will run for up to 12 years. It will compare 2 groups of people taking different doses of aspirin and another group taking dummy tablets.
Risks and benefits
When researchers are looking for a medicine that can lower the risk of a large group of healthy people getting cancer, they also have to look at the risks it carries.
They need to make sure that the benefits outweigh any harm the medicine might cause. This is because many people having the preventative treatment would never develop cancer anyway. In the research studies so far, 2 or 3 people out of 1000 taking aspirin would die of strokes, bleeding or stomach ulcers. But 17 out of 1000 lives would be saved because people would avoid having cancer or heart attacks.
The benefit of aspirin is not seen in people younger than 50. The benefit starts at the age of 50.
Questions we need to answer about aspirin
So there are still some unanswered questions about aspirin and cancer. We need to know which dose works best to lower the risk of cancer developing or spreading, while causing the least harm.
We also need more research to find out:
- how long people should take aspirin for
- what age people should start taking it
- whether some people are more likely than others to get side effects
- whether some people will benefit and others won’t
- whether we can lower the risk of having a stroke when people stop taking aspirin
Lowering your risk of cancer
Remember, there are other things you can do to lower your risk of developing cancer. These include:
- eating a healthy diet
- keeping to a healthy weight
- giving up smoking
- drinking less alcohol