People with Lynch syndrome should be offered aspirin to reduce their risk of colorectal cancer, the UK’s National Institute for Health and Care Excellence (NICE) is recommending.

The draft NICE guidance, currently out for consultation, recommends that aspirin use for at least two years be considered in people with Lynch syndrome  – also known as hereditary non-polyposis colorectal cancer (HNPCC) –  despite finding only low quality evidence supporting its use.

However the committee concluded the potential benefit in a high-risk population likely outweighed potential harms of aspirin such as peptic ulcer, gastrointestinal bleeding or cerebral haemorrhage.

“The optimal dose of aspirin that balances the benefits of aspirin as prevention of colorectal cancer and the potential increased bleeding risk especially with higher doses remains unclear and the committee was not able to recommend a dose, though an ongoing trial is currently studying this. A commonly used dose in current practice is either 150 mg or 300 mg,” the guidance said.

Australian cancer guidelines already recommend people with Lynch Syndrome begin aspirin once they start colonoscopy screening, usually at age 25 years. While 600 mg/day has been shown to be effective, lower doses of 100 mg/day may be as effective, the guidelines said.

Lead author of the guidelines Professor Finlay MacRae told the limbic Australians were the world leaders in terms of advocating for aspirin chemoprevention and it is already widely used in this context..

Australia is one of the countries contributing to an international clinical trial of 1,800 Lynch syndrome carriers to answer the question of optimal dose, he noted.

However  it will be 8-10 years before the cancer outcomes were available from that trial.

Professor MacRae said active consideration of low-dose aspirin (100–300 mg/day) is also recommended in Australia for people aged 50–70 years at average risk of colorectal cancer.

“That is still well substantiated in terms of evidence,” he said.

However the unanticipated mortality outcomes of the ASPREE trial had “stirred the pot”.

“In fact there was a slightly worse outcome in terms of bowel cancer in the aspirin takers,” he said.

However most advocates for aspirin believed the cancer benefits outside Lynch syndrome would take about 10 years to appear.

“…and the ASPREE trial was reporting at about 4.7 years so it was too early to substantiate the benefits,” said Professor MacRae.

“It has led to a pretty strong recommendation that people should not start taking aspirin once they are over the age of 70 years. The Australian recommendation has always been 50-70 years as they are more likely to have side effects from aspirin as they get older.”