Can aspirin stop my cancer spreading?

Aspirin might prevent some cancers and lower the risk of it spreading. But we need more research.

Should I take aspirin?

At the moment, there are no national guidelines for the general population to use aspirin as a way to prevent cancer. Or to stop cancer from spreading. There are still many questions we need to answer.

There is some evidence showing that aspirin may help to prevent some cancers. Also, it might lower the risk of it spreading. But it’s too early to say that everyone, particularly people with cancer, should start taking aspirin.

The National Institute for Health and Care Excellence (NICE) has made suggestions in draft guidance. They say that people with Lynch syndrome (LS) should take aspirin daily to reduce the risk of bowel (colorectal) cancer. LS is a genetic condition that makes people more likely to develop certain cancers, including bowel cancer.

Risks and benefits

Researchers have to look at the risks of all medicines. Particularly so if a medicine can lower the risk of getting cancer in a large group of healthy people.

They need to make sure that the benefits outweigh any harm the medicine might cause. Many people having the treatment as prevention, will never develop cancer anyway.

There are risks with taking aspirin. It 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. This is 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:

  • asthma
  • stomach ulcers
  • haemophilia – a type of blood clotting disorder

Systematic review

Researchers did a systematic review of observational studies in 2018.  A systematic review means that a group of experts gather all the evidence about a particular subject. They then go through it to work out whether there is any evidence to support it.

The review found that we need more information on the best dose of aspirin to treat cancer. Future research should also look at the following information of patients:

  • age
  • body weight
  • smoking
  • personal factors

The researchers said that we need more information on the bleeding caused by aspirin. This can be a serious and deadly risk.

Talk about the risks and benefits with your doctor if you’re thinking of taking aspirin. If your doctor says that 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 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

Research studies show that aspirin might lower the risk of:

  • certain cancers
  • dying from cancer
  • cancers spreading to other parts of the body

The 2018 systematic review found that aspirin might work as an additional treatment for cancer of the:

  • colon (large bowel)
  • breast
  • prostate

But the researchers suggested that we need more research.

As aspirin can cause serious side effects for some people, we need to know whether the benefits of taking it always outweigh the risks. But researchers are looking at the best ways of using aspirin to treat and prevent cancer. These studies include:

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 2023. It is comparing 2 main groups of people. One group takes either a low dose or high dose of aspirin and another group takes dummy tablets.

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. But results are not yet available.

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.

Researchers want to find out if blocking platelets may affect how cancer spreads. This study closed in 2019. Results are not yet available.

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
  • enjoy the sun safely
  • be more active
Last reviewed: 
16 Jan 2020
  • Cancer Research UK Clinical Trials Database

    Accessed January 2020

  • Offer daily aspirin to those with inherited genetic condition to reduce the risk of colorectal cancer

    National Institute for Health and Care Excellence (NICE)

    Accessed January 2020

  • Associations between aspirin use and the risk of cancers: a meta-analysis of observational studies

    Y Qiao and Y Gan

    BMC Cancer 18, 288 (2018)

  • Systematic review update of observational studies further supports aspirin role in cancer treatment: Time to share evidence and decision-making with patients?

    P Elwood and others

    PLoS ONE, 2018, 13(9): e0203957

  • Estimates of benefits and harms of prophylactic use of aspirin in the general population

    J Cuzick and others

    Annals of Oncology, 2015. Vol 26, Issue 1

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact with details of the particular issue you are interested in.

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