The United States Food and Drug Administration (FDA) has approved Evista® (raloxifene) to prevent invasive breast cancer among postmenopausal women with osteoporosis and postmenopausal women who are at a high risk of developing breast cancer.
Breast cancer is diagnosed in over 200,000 women annually in the United States and is responsible for approximately 40,000 deaths. The majority of women with breast cancer have cancer that is estrogen-receptor positive (ER-positive). This type of breast cancer is stimulated to grow by the female hormones estrogen and/or progesterone.
Women with ER-positive breast cancer are commonly treated with hormone therapy. This approach suppresses the formation of estrogen or blocks estrogen from stimulating cancer cells to grow.
Some postmenopausal women at a high risk of developing breast cancer can be treated with the anti-estrogen agent tamoxifen. Results from studies have indicated that tamoxifen can reduce the risk of developing breast cancer in these high-risk women by approximately 50%.
However, serious side effects associated with tamoxifen may prevent physicians from recommending its use as a preventive agent or may stop patients from taking tamoxifen for breast cancer prevention. These side effects include an increased risk of endometrial (uterine) cancer and the development of blood clots.
Tamoxifen is widely used in the treatment of ER-positive breast cancer; the drug’s benefits outweigh its risks in this setting. However, a newer class of drugs that inhibit estrogen’s effects on stimulating cancer growth, referred to as aromatase agents, are being widely used for the treatment of ER-positive breast cancer, as outcomes are improved with aromatase agents over tamoxifen in this disease.
Evista is an agent that also reduces the stimulatory effects of estrogen on cancer growth. It was previously approved for the prevention and treatment of osteoporosis. However, due to the fact that it reduces estrogen’s effects on cells, researchers speculated that it may also be used as a preventive or therapeutic agent for ER-positive breast cancer.
The trial that prompted FDA approval for Evista in the prevention of breast cancer was referred to as the STAR trial. The STAR trial directly compared Evista to tamoxifen in the prevention of breast cancer in women who were considered at a high risk of developing the disease. This trial included over 19,000 women who were considered high risk due to the following factors: a family history of breast cancer, personal medical history, age, age at first menstrual period, and age at first live birth. Women were followed for nearly four years.
- Evista produced results equal to tamoxifen in reducing the risk of developing breast cancer among these women. Evista, however, had fewer side effects than tamoxifen.
- Rates of breast cancer were reduced by approximately 50% in both groups of patients.
- Among women who had not had a hysterectomy (approximately half of the women), those treated with Evista had a 38% lower rate of uterine cancer than those treated with tamoxifen.
- Women treated with Evista had a 29% reduced risk of developing blood clots compared with those treated with tamoxifen.
- Women treated with Evista had an approximately 20% reduced risk of developing cataracts compared with those treated with tamoxifen.
- Women treated with tamoxifen had fewer cases of lobular carcinoma in situ (LCIS) and ductal carcinoma in situ (DCIS)-conditions considered to be “pre-cancerous”-than those treated with Evista.
Post menopausal women who are either at a high risk of developing breast cancer or who have osteoporosis may wish to speak with their physician regarding their individual risks and benefits of receiving tamoxifen for the prevention of breast cancer. However, because all medications carry their own side effects and risks, it is important that each woman considering taking Evista understand side effects associated with this agent.
Reference: Eli Lilly. FDA Approves Lilly’s Osteoporosis Drug EVISTA® (raloxifene HCl) to Reduce The Risk of Invasive Breast Cancer in Two Populations of Postmenopausal Women. Available at: http://newsroom.lilly.com/ReleaseDetail.cfm?ReleaseID=264036. Accessed September 2007.