Drugs like aspirin can reduce the risk of breast cancer by about 20 per cent, according to a review of studies published over the past 27 years.

Scientists analysed 21 studies involving more than 37,000 women and found an overall decreased risk for women taking nonsteroidal anti-inflammatory drugs (NSAIDs). They also discovered that they could play a role in treating women already diagnosed with breast cancer.

However, the researchers cautioned that more studies were needed on the ideal type of drug, dose and duration before there was any big push to get women to take the drugs routinely.

They also warned that more research was needed on whether any benefits outweighed side-effects in the long term. They concluded: "There may be a role for NSAIDs in combination with endocrine therapies as either an adjuvant or palliative treatment for women with established breast cancer."

Ian Fentiman, professor of oncology at Guy's and St Thomas' NHS Foundation Trust in London, carried out the study, published in the International Journal of Clinical Practice. He said: "Our review suggests that, in addition to possible prevention, there may also be a role for NSAIDs in treatment of women with established breast cancer. NSAID use could be combined with hormone therapy."

"NSAIDs may well offer protection against developing breast cancer in the first place and may provide a useful addition to treatment available to women who already have the disease. Recent studies of NSAIDs use have shown about a 20 per cent risk reduction in incidence of breast cancer, but this benefit may be confined to aspirin use alone and not other NSAIDs."