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 in people with a family history of the disease by 60%.
There was also evidence of a similar impact on other solid cancers with the same genetic link.
The findings, from a University of Newcastle study, 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 600 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.
CAPP2 involved scientists from 43 centres in 16 countries, including the UK.
The findings can be found in an online edition of The Lancet medical journal.