Raloxifene therapy reduces the risk of breast cancer in post-menopausal, osteoporotic women, regardless of lifetime estrogen exposure; however, the reduction is greater in women with a higher lifetime estrogen exposure, according to the results of a recent study published in the

Journal of Clinical Oncology.

Breast cancer is the second leading cause of cancer death in women in the United States, with approximately 200,000 cases diagnosed each year. Although several risk factors have been associated with breast cancer, the cause of the majority of cases of breast cancer remains unknown. As researchers continue to explore the causes of this disease, they also uncover factors that may prevent the development of breast cancer. Often, lifestyle changes and choices can help reduce the risk of cancer.

Breast cancers are classified as estrogen receptor-positive or estrogen receptor-negative. Estrogen receptor-positive breast cancer is characterized by the overabundance of estrogen receptors to which estrogen binds and facilitates cellular growth and replication. Anti-estrogens are drugs that block these estrogen receptors, thereby preventing the estrogen-stimulated growth of the breast cancer cells.

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Raloxifene is a selective estrogen receptor modulator (SERM) that has been approved by the FDA for the treatment of osteoporosis in postmenopausal women. The Multiple Outcomes of Raloxifene Evaluation (MORE) study was a double blind, placebo-controlled, randomized clinical trial designed to evaluate the effects of long-term raloxifene therapy for the treatment of osteoporosis in postmenopausal women. An additional secondary end point of the trial was the incidence of breast cancer.

The study involved 7,705 postmenopausal women up to 80 years old with osteoporosis who were randomly assigned to receive either placebo, 60 mg of raloxifene a day or 120 mg of raloxifene a day for four years. The researchers then analyzed the relationship between breast cancer incidence and baseline characteristics that indicated estrogen exposure, such as previous hormone replacement therapy, prevalent vertebral fractures, family history of breast cancer, bone mineral density (BMD), body mass index and age at menopause. At the end of the 4-year trial, 77 women had primary breast cancer, with 61 of these cases being categorized as invasive.

The results of the study indicated that increased lifetime estrogen exposure increases the risk of developing breast cancer. Women with the highest one-third estradiol levels had 2.07-fold increased risk of developing invasive breast cancer when compared with women with lower levels. Furthermore, the results indicated that raloxifene reduces breast cancer risk in postmenopausal women with osteoporosis, especially in those with higher lifetime exposures to estrogen. Raloxifene significantly reduced the risk of breast cancer in both the low and high estrogen groups for all risk factors examined; however, the women with the highest lifetime exposure to estrogen experienced a significantly greater benefit from raloxifene.

The researchers concluded that raloxifene reduces the risk of breast cancer in postmenopausal women with osteoporosis regardless of lifetime estrogen exposure, but was especially beneficial to those with high lifetime estrogen exposure. Research is ongoing to determine the relationship between raloxifene and breast cancer risk. Women who are at a high risk for developing breast cancer may wish to speak with their physicians about the risks and benefits of participating in a clinical trial in which raloxifene and other promising new screening techniques are being evaluated. Two sources of information about ongoing clinical trials include clinical trials listing services provided by the National Cancer Institute (cancer.gov) and eCancerTrials.com. eCancerTrials.com also performs personalized clinical trial searches on behalf of patients. (Journal of Clinical Oncology, Vol. 19, No. 12, pp. 3111-3116, 2001)

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