Both drugs have also been shown to lower levels of the cholesterol associated with heart disease. In the first breast cancer prevention trial, scientists found that tamoxifen increased a women's chances of three rare but life-threatening health problems. Blood clots are also a possible side effect of raloxifene, but this drug does not increase the risk of endometrial cancer. However, raloxifene is limited to women who have passed menopause because it has never been tested on premenopausal women. Raloxifene could offer a safer and equally effective prevention drug that may also prove to have other life-saving benefits.
Tamoxifen is currently the most widely prescribed cancer drug in the world.
Raloxifene received FDA approval in the United States in January 1998 and is also approved in several other countries for osteoporosis prevention. Of the 22,000 women in STAR, half will receive tamoxifen, while the other half will receive raloxifene. The trial is a double-blind study, meaning that neither the doctor nor the patient will know which drug is being administered. Only postmenopausal women at increased risk of developing breast cancer are eligible for the study. Breast cancer is the most common type of cancer among women in the United States.