The FDA approved tamoxifen in 1998 to reduce the incidence of breast cancer in women at increased risk for the disease. Tamoxifen works against breast cancer, in part, by interfering with the activity of estrogen, a hormone has been shown to promote the growth of breast cancer cells. Raloxifene also is an oral medication, taken in pill form. It received FDA approval in 1997 for the prevention of osteoporosis in postmenopausal women. During studies into its ability to prevent osteoporosis, researchers also found that women taking raloxifene developed fewer breast cancers than women taking a placebo did.
Breast cancer arises over many years.
We know that it is, initially at least, a slow-growing disease. Participants will be counseled about the potential benefits and risks of the two drugs. Women taking tamoxifen in clinical trials had an increased risk of endometrial cancer, blood clots and stroke. Information on side effects associated with raloxifene is limited because it has not been studied as extensively as tamoxifen. Researchers have found that women taking raloxifene had an increased risk of developing serious blood clots.