Aspirin, one of the world's oldest and cheapest drugs, has shown remarkable promise in treating colon cancer in people with mutations in a gene that's thought to play a role in the disease.
Among patients with the mutations, those who regularly took Aspirin lived longer than those who didn't, a major study found. Five years after their cancers were diagnosed, 97 per cent of the Aspirin users were still alive versus 74 per cent of those not taking the drug.
Aspirin seemed to make no difference in patients who did not have the mutations.
This sort of study can't prove that the drug 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. 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. He and others from Harvard Medical School led 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.
Several studies suggest that Aspirin may help fight cancer, especially colorectal tumours. It is often recommended for people who have colon cancer and others at high risk of developing it. But it's not advised for wider use, or for cancer prevention, because it can cause serious bleeding in the stomach and gut.
What has been lacking, doctors say, is a good way to tell which people might benefit the most, so Aspirin's risks would be justified. Chan's study suggests a way to do that.