Aspirin and cancer
Aspirin might lower the risk of getting some cancers. It may also prevent some cancers from spreading, or people dying from it. But we need more research.
Should I take aspirin?
Aspirin is a drug commonly used to relieve pain, 
and fever. It is also used as a blood thinner.
There is some evidence showing that aspirin may help lower the risk of:
- getting some cancers
- cancer spreading
- people dying from cancer
But, at the moment, there are no national guidelines for the general population to take aspirin to prevent or treat cancer.
Lynch syndrome
The National Institute for Health and Care Excellence (NICE) recommends daily aspirin for people with Lynch syndrome. This is to reduce the risk of bowel cancer. Lynch syndrome is a genetic condition. It makes people more likely to develop certain cancers, such as bowel cancer and womb cancer.
Certain medical conditions
Doctors prescribe low dose aspirin for some people with cancer who have heart and blood vessel (vascular) problems. This includes conditions such as:
- polycythaemia vera
- essential thrombocythaemia
- primary myelofibrosis
myeloma – in some peopleprostate cancer - people treated with a type of hormone therapy called diethylstilbestrol
Results from studies so far
In 2021, researchers published a and . It included 118 observational studies. Observational studies aim to find out what happens to people in different situations. The studies included people with18 different cancer types. About 250, 000 people with cancer in the review were taking aspirin.
It showed that anytime after diagnosis about 20 out of every 100 (20%) more people with cancer who take aspirin are likely to be alive. This is when compared with those not taking aspirin. The review also found that aspirin can help to reduce the risk of cancer spreading. But researchers can’t say yet that all people with cancer should start taking aspirin.
The same researchers say evidence shows aspirin can be used as an extra treatment for several cancers. But it is not an alternative to any other treatment. There are still questions that need answering.
Other trials have also shown the need for further research on aspirin and cancer. One trial found that aspirin did not help to prevent breast cancer from coming back (recurrent breast cancer).
There is also research on people older than 70 taking a daily low dose of aspirin. The results showed that aspirin had an unclear benefit versus risk balance. We need more research to find out which groups of people with cancer, who are over 70, should either:
- start taking aspirin
- stop taking it if they are already doing so
Risks when taking aspirin
There are risks with taking aspirin, as there are with all medicines. It can cause serious side effects for some people, such as internal bleeding. There are also other reasons why some people can’t take aspirin, for example, due to other health conditions (contraindications).
Some people with cancer already have a higher than normal risk of bleeding. Others might have a higher risk of developing blood clots. This is because of their cancer or treatment.
Bleeding caused by aspirin can be a serious and deadly risk. But the systematic review and meta-analysis of 2021 found that the risk of bleeding from aspirin might be less severe. This is when compared to bleeds that just happen (spontaneous bleeds). The review also found that bleeding from aspirin rarely causes death.
Some cancer drugs can also cause significant side effects when taken with aspirin. Aspirin can cause severe complications in people with other medical conditions such as:
- asthma
- stomach ulcers
- haemophilia – a type of blood clotting disorder
Talk about the risks with your healthcare team if you’re thinking of taking aspirin. If your doctor says you can take aspirin, always eat something before taking it. Taking aspirin with food protects your stomach and lowers the risk of bleeding.
The dose of aspirin
In many trials so far, 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 to help reduce the risk of cancer. Nor to prevent cancer from spreading or people dying from it. But, as with any drug, it’s important not to take too much because you could increase your risk of severe side effects.
Current research studies looking into aspirin and cancer
A few trials are looking into whether aspirin might work as an extra treatment for cancer. Two small trials on stomach and ovarian cancer have already given early results. Although aspirin was safe to use, neither trial showed any benefits against cancer.
There are some cancers for which there are no trials at the moment. These include cancers such as cancer of the or cancer of unknown primary (CUP).
Talk to your healthcare team about taking aspirin for your cancer type.
Researchers are also looking at aspirin:
- to stop and delay cancer from coming back
- to find the best possible dose
- with other drugs
ADD-Aspirin trial
Cancer Research UK is helping to fund the world's largest clinical trial looking at aspirin as a way 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 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:
- bowel
- breast
- oesophagus (food pipe)
- prostate
- stomach
The trial is running until 2025. It compares 2 main groups of people. One group takes either a low or high aspirin dose, and another takes dummy tablets (placebo).
A trial looking at different doses of aspirin for people with Lynch syndrome (CAPP3)
The CAPP2 trial showed that aspirin reduced the risk of cancer in people with Lynch syndrome. But in a small number of people, aspirin can cause bleeding in the stomach. This happens more often when people take higher doses of aspirin. So, researchers wanted to see if lower doses of aspirin work as well.
The CAPP3 trial aims to find the best dose of aspirin to prevent cancer in people with Lynch syndrome. This trial closed in 2019. We expect results in 2024 or 2025.
Aspirin and ticagrelor
Aspirin and a drug called ticagrelor block platelets. Platelets are blood cells. They help the blood to clot when there is an injury. Researchers know that circulating cancer cells interact with platelets in the blood. This may help protect the cancer cells and spread them throughout the body.
Results from this trial showed that ticagrelor as a treatment on its own worked better than aspirin to prevent cancer cells from interacting with platelets. The researchers said that we need more research.
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. This dose must cause 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
Lowering your risk of cancer
Remember, there are other things you can do to lower your risk of developing cancer. These include:
- giving up smoking
- eating a healthy diet
- keeping to a healthy weight
- drinking less alcohol
- enjoying the sun safely
- being more active
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