Many thousands of hereditary cancers and deaths could be prevented simply by taking aspirin, a landmark study has found.
Two pills a day cut the long-term risk of bowel cancer by 60pc in people with a family history of the disease.
There was also evidence of a similar impact on other solid cancers with the same genetic link.
The findings suggest aspirin treatment could prevent up to 10,000 cancers over the next 30 years and possibly save 1,000 lives.
Despite taking large doses of aspirin -- two 300 milligram pills per day -- patients taking part in the study suffered no undue adverse effects.
Aspirin is known to raise the risk of internal bleeding and stomach ulcers, as well as certain kinds of stroke.
But, according to the researchers, it could be a risk worth taking for people with a high cancer susceptibility.
A new investigation is planned which will look more closely at what doses of aspirin are needed to prevent cancer.
The study, called CAPP2, provides the most definitive evidence yet of aspirin's anti-cancer properties.
It focused on patients with Lynch syndrome, a genetic fault that strongly predisposes people to bowel cancer and a number of other solid organ cancers.
Around one in 1,000 members of the general population carry the defective genes, which account for one in 30 cases of bowel cancer. Other diseases linked to Lynch syndrome include womb, ovarian, pancreatic, brain, stomach and kidney cancers.