The study shows that regularly taking the medicine cuts the risk of bowel cancer by more than 60% in those with a particular genetic predisposition to get the disease – as well as reducing the risk of other hereditary cancers.
Scientists who led the study said people with several family members with cancers other than breast, blood and prostate might be advised to start taking aspirin daily from the age of 45.
They said those without a family history of the disease might also consider doing so, but that they should make a personal assessment of the risks and benefits and get medical advice. Anyone thinking of taking the drug regularly should consult their doctor first.
Doctors already prescribe low, daily doses of aspirin to people at increased risk of heart attacks and strokes, and evidence has been growing of anti-cancer properties for 20 years. However, this is the first long-term, randomised controlled trial to show such an effect.
The trial involved people with Lynch syndrome, a genetic abnormality that predisposes carriers to develop bowel cancer and other solid organ cancers including endometrial, ovarian, stomach, kidney, oesophageal, brain and skin tumours.
The condition affects at least one in 1,000 people. Carriers are around 10 times as likely to develop cancer and often do so at a young age.
Professor John Burn of Newcastle University, who led the study, estimated that if all 30,000 or so people with Lynch syndrome in the UK were to start taking two aspirin tablets a day then some 10,000 cancers would be prevented over the next 30 years, saving about a thousand lives. The downside of the treatment is that around an extra thousand people would develop stomach ulcers as a side-effect.
“People with a genetic susceptibility are a model system,” said Burn, whose work is published online in the Lancet on Friday. “They are more sensitive to the environmental triggers to cancer.
“If we can do something to change cancer progression in people at high genetic risk, then that’s telling us what we might all benefit. But we are not making a recommendation for the general population. Everyone can take this evidence and make their own choice.
“In between you have the people who have a family history [of cancer]. Those individuals may well decide to put themselves on aspirin and that would be a reasonable conclusion from the data currently available.”
Between 1999 and 2005, about half of a group of 861 Lynch syndrome carriers were given two aspirins (600mg) a day, while the rest took placebos.
By 2010 those who had taken aspirin for at least two years were 63% less likely to have developed bowel cancer.
Looking at all forms of the disease, almost 30% of those in the placebo group developed a Lynch syndrome-related cancer, compared with 15% for those given aspirin.
The most common side effects associated with taking aspirin are gastrointestinal ulcers and stomach bleeding. There is also an very small increased risk of haemorrhagic stroke, in which a blood vessel in the brain bursts.
There was no difference in the proportions of the study groups suffering such side-effects.
Burn added that he takes low-dose aspirin tablets as a preventative measure. “That was a balanced judgment based on weighing risks and benefits. I know I might get an ulcer or a cerebral bleed but I’d rather not have a heart attack, stroke or cancer. That’s my choice.”
Aspirin is a synthetic version of the active component of willow bark, salicylic acid, which has been used as a medicine for its anti-inflammatory properties for hundreds of years. Salicylates also trigger programmed cell death to help diseased plants contain the spread of infection.
“It’s not a huge stretch to think that if salicylate induces programmed cell death in plants to kill infected cells, maybe it’s doing similar things in the animal kingdom to enhance the death of aberrant cells causing cancer,” said Prof Burn.
“This adds to the growing body of evidence showing the importance of aspirin, and aspirin-like drugs, in the fight against cancer and emphasises how critical it is to carry out long-term international research,” said Prof Chris Paraskeva, a bowel cancer expert at the University of Bristol.
The CAPP team have launched a website to recruit 3,000 people with Lynch syndrome worldwide to take part in a five-year trial to determine the best dose of aspirin to take.
- Should aspirin be used to prevent cancer? (eurekalert.org)
- Lynch Syndrome (familyhistorybowelcancer.wordpress.com)
- Aspirin cuts cancer risk in people with an inherited susceptibility (familyhistorybowelcancer.wordpress.com)
- PIK3CA mutation in Colorectal Cancer may serve as a Predictive Molecular Biomarker for adjuvant Aspirin therapy (pharmaceuticalintelligence.com)
- A dedicated service for the Management of Hereditary Colorectal Cancer Improves Adherence with Molecular Testing for Lynch Syndrome (familyhistorybowelcancer.wordpress.com)