CaPPtain’s Blog: John Burn, August 2026

It's been a long time since my last update but 2 years on from the last CaPP3 participant reaching their fifth anniversary we have now published the first results of our aspirin study. The take home message is that the people who took 75mg aspirin were as well protected as those who took 600mg and had fewer side effects. The UK Cancer Genetics Group of the British Society for Genetic Medicine support the recommendation that people with Lynch syndrome should take a daily "baby aspirin".

We think that people carrying extra weight need a bigger dose. We are recommending people with a BMI over 30 should take 150mg (two baby aspirins) a day.

Side effects of aspirin increase as we get older. The protection of taking aspirin last for several years after stopping. On balance we think people should stop taking aspirin at 70 unless they need it because of a risk of heart attacks.

Many people have a low grade infection in their stomach with a bug called H pylori. It increases the risk of ulcers when you take aspirin. A simple test can tell and antibiotics can clear the infection.

Very rarely people have small swellings on blood vessels called aneurysms. These can burst and if a person is taking aspirin they bleed longer. This is a major problem if it happens inside the brain. In most cases, high blood pressure causes aneurysms to leak so we recommend that people about to take aspirin should have their blood pressure checked and treated if needed.

With these precautions, the benefits for people with Lynch syndrome are clear. We are working to get aspirin listed as in the British National Formulary as a treatment for people with Lynch syndrome. There are plans in England to write to all GPs with a patient with Lynch syndrome in the next few months to tell them about the new guidance.

Meanwhile we will continue to follow the records of all the people in CaPP3 to collect a record of all cancers for at least 10 years from starting the aspirin. This will make the statistics more certain and will give us the information we need to check how much aspirin is needed for people carrying extra weight.

We are also working on a simple urine test to check if people are taking enough aspirin. The urine test is looking at a chemical that leaks from platelets. These are the small blood cells that fix small leaks. They can also cause clots. Aspirin blocks platelets and prevents clots. It also reduces the chemical, called thromboxane, that we think prevents the immune system from attacking cancer cells.