Scientists have produced yet more strong evidence of the cancer-fighting properties of the commonly used painkiller aspirin.
Aspirin: A wonder drug?
Earlier this week the drug was reported to cut the risk of developing mouth and throat cancers.
Now two teams of US scientists have found that it can also significantly reduce the risk of colorectal cancer in high risk patients.
Regular use of the drug appears to reduce the chances of developing pre-cancerous growths in the colon which often lead to cancer.
However, the researchers warned that more work would be needed to assess possible side-effects of long-term aspirin use.
Aspirin had a significant protective effect
Dr Richard Schilsky, from the University of Chicago who led one of the research teams, said the protective effect of taking just one aspirin a day was so great his trial was stopped early.
He said: "Aspirin had a significant protective effect.
"It clearly reduced the formation of polyps in this study of high-risk individuals, which is good news because it provides a new way to lower the risk of recurrence in patients who have had colon cancer."
Better all round
The researchers found that an aspirin a day reduced the occurrence of precancerous polyps called adenomas by about one-third in patients with a history of colorectal cancer.
Patients on aspirin who did get polyps took longer to develop them, and they had fewer polyps than those not taking aspirin.
The two studies looked at slightly different groups of patients.
One focused on patients who had previously had surgery for colorectal cancer but appeared to be cured. These people are very likely to develop new adenomas, which often progress to cancer.
The other looked at people who had previously had precancerous polyps removed, but who had not been diagnosed with colorectal cancer.
The first study tested aspirin at a dose of 325 milligrams but the second study produced more effective results on a dose of just 80 milligrams.
It is thought that aspirin cuts the risk of cancer by blocking the action of an enzyme essential to the growth of tumours.
If so, this could mean that aspirin may have a similarly beneficial effect on other cancers of the digestive system.
The research is published in the New England Journal of Medicine.