A major British study found that taking aspirin regularly can reduce the long-term risk of cancer by 60%.
Researchers found that aspirin can reduce the risk of cancer by 60% in people with a family history of the disease.
The huge study covered 16 countries and is the first proof that aspirin has a preventive action that is likely to benefit anyone using it every day.
Many people who take low-dose aspirin to prevent heart disease will gain from its anti-cancer properties, while healthy people may follow the example of increasing numbers of doctors who take it for insurance.
The study included 861 patients with Lynch syndrome, a genetic fault leading to bowel and other cancers at an early age, half of them were given two aspirins a day, 600 mg in total, for two years.
The rest of the patients included in the study were given placebo, or dummy, pills, says a report published online in The Lancet medical journal.
Initially, the researchers found no change in cancer rates between the groups. However, when they followed up the study after 5 years, they detected a significant difference.
By 2010, the researchers had identified a total of 19 new bowel cancers among those given aspirin and 34 among the placebo group, a cut of 44% among patients taking the drug.
Then, researchers focused on the 60% of patients who they were certain had conscientiously taken aspirin for at least two years they found an even more striking result.
In that group, only ten cancers were discovered compared with 23 in the placebo group, a cut of 63%.
Rates of other cancers linked to Lynch syndrome were almost halved by taking aspirin.
Professor Sir John Burn from Newcastle University, who led the research, said:
“What we have finally shown is that aspirin has a major preventive effect on cancer but it doesn’t become apparent until years later.”
The study is being hailed as the last piece of the jigsaw after years spent trying to prove that aspirin has a direct effect in stopping tumours.
A big step forward came last year with a study which showed that low-dose aspirin cuts overall death rates by a third after five years’ use.
However, it used records to look at the incidental benefits for patients taking it to stave off further heart attacks and strokes. The latest trial actually set out to prove that cancer could be prevented in people taking it for no other reason.
According to experts, healthy middle-aged people who start taking aspirin around the age of 45 or 50 for 20 to 30 years could expect to reap the most benefit because cancer rates rise with age.
There is widespread concern that side-effects such as stomach bleeding and haemorrhagic stroke outweigh any advantage among healthy people.
Prof. Burn, who takes aspirin every day, estimates there are 30,000 people with Lynch syndrome in the UK who might benefit from aspirin treatment.
“If we put them all on two aspirins a day now, in the next 30 years or so we would prevent 10,000 cancers. On the other hand, this would cause around 1,000 ulcers.
“If we can prevent 10,000 cancers in return for 1,000 ulcers and 100 strokes, in most people’s minds that’s a good deal, especially if you’ve grown up in a family with three, four, five, six people who have had cancer.
“On the other hand, if you’re just in the general population and you don’t have cancer in your family, then that’s going to be a much finer balance.”
According to Prof. Burn, further research will take place to discover the ideal dose of aspirin.