A new international drug trial aimed at preventing breast cancer in high-risk women has been launched.
Anastrozole, which is made by AstraZeneca under the brand name Arimidex, has already been shown to be as effective, or better, at tackling breast cancer than the drug tamoxifen.
Researchers will now test Anastrozole against a placebo in 10,000 older women who have twice the normal risk of breast cancer to see if it can stop the disease from developing. The 10-year trial, called Ibis II, will run from 40 centres worldwide.
Professor Jack Cuzick, of the charity Cancer Research UK and the University of London, said the new trial could have a dramatic impact on the disease, reducing the risk by up to 50 per cent.
In an earlier study, tamoxifen, which is the standard hormone treatment for oestrogen-sensitive tumours, was shown to reduce the incidence of breast cancer by a third in women at a higher risk of the disease.
Anastrozole belongs to a class of drugs called aromatase inhibitors that suppress the production of the female hormone oestrogen in post-menopausal women. It is believed to have fewer side effects than tamoxifen, which can cause blood clots, hot flushes and increases the risk of endometrial cancer.
Breast cancer is the most common cancer in women with more than one million cases diagnosed worldwide each year. More than 13,000 women die from the disease every year in the UK.