US scientists have found that taking an aspirin a day could reduce a woman's risk of developing the most common kind of breast cancer.
Aspirin has already been proved to combat pain, rheumatoid arthritis, heart disease, strokes and some cancers, notably those of the lung, bowel and pancreas.
Now for the first time it has been shown to lower the risk of oestrogen-sensitive breast cancer, which causes 75% of tumours.
A large study by the National Cancer Institute, Rockville, Maryland, involving 127,000 women found that aspirin was linked to a small reduction in the risk of having this form of the disease.
The women, aged 51-72, were enrolled into the National Institutes of Health AARP Diet and Health Study, a major US investigation into links between diet, behaviour and cancer.
Aspirin belongs to a class of medicines known as non-steroidal anti-inflammatory drugs (NSAIDs). The researchers found that NSAID use generally had no influence on overall susceptibility to breast cancer. But daily doses of aspirin resulted in a 16% reduction in risk for oestrogen-positive breast cancers.
Aspirin and other NSAIDs block cyclo-oxygenase (COX) enzymes, biological catalysts which may affect the growth of cancer.
However, unlike other NSAIDs, aspirin's impact on COX enzymes is irreversible.