Aspirin seemed to make no difference in patients who did not have the mutations.
This sort of study can't prove that aspirin caused the better survival, and doctors say more research must confirm the findings before aspirin can be recommended more widely. The study wasn't designed to test aspirin; people were taking it on their own for various reasons.
Still, the results suggest that this simple medicine might be the cheapest gene-targeting therapy ever found for cancer. About one-sixth of all colon cancer patients have the mutated gene and might be helped by aspirin. And aspirin costs just pennies a day.
"It's exciting to think that something that's already in the medicine cabinet may really have an important effect" beyond relieving pain and helping to prevent heart attacks, said Dr. Andrew Chan, of Massachusetts General Hospital, an author of the study, which appears in Thursday's New England Journal of Medicine.
Cancers of the colon or rectum are a leading cause of cancer deaths worldwide. More than 140,000 new cases and 51,000 deaths from them are expected this year in the United States.