Tests begin on breast cancer prevention drug

Scientists launched an international trial Tuesday to determine if a drug used to treat breast cancer can prevent the disease in high-risk women. Anastrozole, made by AstraZeneca under the brand name Arimidex, has already been shown to be as good or better than the drug tamoxifen in a trial of older women with hormone-sensitive tumors. Researchers will now test it 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. Jack Cuzick, of Cancer Research U.K. and the University of London, said the new trial could have a dramatic impact on the disease and could reduce the risk of hormone-sensitive breast tumors by more than 50%. "It is about 1-1/2 times as good as tamoxifen in terms of treatment," he told a news conference marking the launch the trial, which will be run from 40 centers worldwide. In an earlier study tamoxifen, which is the standard hormone treatment for estrogen-sensitive tumors, was shown to reduce the incidence of breast cancer by one third in women at a higher risk of the disease. Anastrozole belongs to a class of drugs called aromatase inhibitors. They suppress the production of the female hormone estrogen in postmenopausal women. Tamoxifen works by preventing the action of estrogen on the cells of the breast. Cuzick, who will lead the international research team, said anastrozole has fewer side effects than tamoxifen--which can increase the risk of endometrial cancer, blood clots, and hot flashes--so more women are able to take the drug. But there was a greater risk of bone fractures with anastrozole. Women in the trial will be closely monitored, and those with low bone density will be given treatments to improve it. Breast cancer is the most common cancer in women, with more than 1 million cases diagnosed worldwide each year. Risk factors include family history of the disease, early puberty, late menopause, delaying childbirth, or not having children. Some studies have suggested that lesbians are also at a higher risk for the disease.