There is some evidence that long-term use of aspirin lowers the risk of developing non-cancerous growths (polyps) and bowel cancer. But aspirin may also cause side effects, such as indigestion or bleeding, and we don’t know how safe it is to take regularly.
Doctors do not usually recommend taking aspirin regularly for bowel cancer prevention unless you have a condition called Lynch Syndrome, or you’re taking part in a clinical trial. If you’re thinking of taking aspirin, speak to your GP or cancer specialist first. They can advise you on the safety of aspirin and whether it might benefit you.
How aspirin affects cancer risk
Some research studies show that people who take aspirin regularly, for three years or more, have a lower risk of getting cancer of the bowel, oesophagus (food pipe or gullet) and stomach. There is also some weaker evidence of reduced risk of breast, prostate and lung cancers.
Aspirin may also benefit people who have already been diagnosed with bowel cancer that has not spread to other parts of the body. A small number of studies have found that it reduces the risk of bowel cancer coming back after treatment but more research is needed to back this up.
Research also shows that aspirin reduces the risk of bowel cancer in people who have Lynch syndrome. Guidelines from the BSG (British Society of gastroenterology) recommend that everyone with Lynch syndrome should take aspirin daily. More research is needed to work out the most effective dose.
Aspirin may also give extra benefit to people with Lynch syndrome who are overweight, and so these people may benefit from higher dosages. Some people with Lynch syndrome have an even higher risk of bowel cancer if they are very overweight. Aspirin may reduce this risk to match that of people with Lynch syndrome who are a healthy weight. The study that found this out involved a small number of people who fit into this group so more research is needed to find out more.
Side effects of aspirin
The most common side effects of aspirin are indigestion and bleeding. Up to one in every ten people (ten per cent) may get more nose bleeds, bleed for longer or bruise more easily. In rare cases, aspirin can cause more serious side effects, like bleeding in the stomach.
You may not be able to take aspirin if you have had other medical problems like asthma, stomach ulcers or problems with your liver, kidneys or heart. Your GP may check if you have bacteria called Helicobacter pylori in your stomach, which can cause stomach ulcers. Getting rid of these bacteria can reduce the risk of stomach ulcers when you are taking aspirin.
Speak to your specialist
We need more information about how aspirin works to lower the risk of bowel cancer, who it might help most, what dosage is best and how long people should take it for. Until we have these answers, doctors can’t recommend that people take aspirin regularly to prevent bowel cancer. If you’re thinking of taking aspirin, speak to your GP or cancer specialist first. They can advise you on the safety of aspirin and whether it might benefit you.
The following clinical trials are currently looking at the effects of aspirin on bowel cancer. If you’re interested in joining a trial, speak to your GP or cancer specialist. You might also like to read our information on taking part in a clinical trial.
This study is looking at the effect of aspirin and a drug called ticagrelor on how cancer spreads. Recruitment has now closed and the trial is ongoing.
This trial is looking at whether aspirin can help stop cancer coming back after treatment in people with early-stage cancer. It is recruiting new people to take part in the trial until the end of September 2021.
This trial is comparing different doses of aspirin, to see the effect on cancer risk in people with Lynch syndrome. Recruitment for this trial has closed and the results are being analysed.
This trial looked at whether taking aspirin or fish oil could be a way of preventing polyps from forming. The results showed that aspirin reduces the number of bowel polyps in people who have had polyps before and are at a higher risk of bowel cancer. Read more about this trial on our blog.
Updated December 2019