STAR Trial: Raloxifene is as Effective as Tamoxifen in Reducing Breast Cancer Risk

May 1, 2006 - Raloxifene, a drug now approved by the FDA for preventing and treating osteoporosis in postmenopausal women, also reduces the risk of developing breast cancer in a particular group of women. In the Study of Tamoxifen and Raloxifene (STAR) clinical trial, 19,747 high-risk postmenopausal women who were at least 35 years old were given either tamoxifen or raloxifene for five years. The results of the trial show that tamoxifen and raloxifene worked equally well in reducing the risk for breast cancer and that raloxifene has fewer side effects associated with its use.

Raloxifene (Evista®) is in the class of drugs called Serum Estrogen Receptor Modulators (SERMs). These drugs block estrogen receptors on breast cancers that are classed as estrogen receptor-positive and help to keep the cancer from growing and spreading. The well-known drug tamoxifen (Nolvadex®, also a SERM) is the only drug now available for high risk pre- and postmenopausal women to reduce their risk for developing invasive breast cancer.

Side effects associated with tamoxifen include cancer of the uterus, blood clots, strokes, cataracts and hot flashes.

Side effects associated with raloxifene include blood clots, leg and joint pain and hot flashes.

The study found that:

• Both tamoxifen and raloxifene were effective and reduced the risk for invasive breast cancer by approximately 50 percent.
• The risks were fewer overall with raloxifene--lower risk of developing uterine cancer and blood clots and no risk of cataracts.
• Both drugs offer protection for the bones.
• Tamoxifen reduces the risk for the non-invasive (sometimes called pre-cancer) lesions, known as lobular carcinoma in situ (LCIS) and ductal carcinoma in situ (DCIS); raloxifene does not.

Komen Foundation Comments

It should be emphasized that this study is about reducing the risk for the occurrence of breast cancer in high-risk postmenopausal women who have not been diagnosed with cancer.

Tamoxifen can be used to reduce the risk for invasive breast cancer in both pre- and postmenopausal women; raloxifene is only indicated for use in post-menopausal women. Raloxifene is not yet FDA-approved for use in high-risk postmenopausal women for breast cancer risk reduction, but it is approved for the prevention and treatment of osteoporosis.

Tamoxifen and the aromatase inhibitor (AI) drugs are currently used as treatments following the diagnosis of breast cancer to reduce the risk of the cancer returning. AIs block the production of estrogen, making it unavailable to the estrogen-dependent cancer cells. AIs are only used in postmenopausal women for this purpose.

These findings could offer high-risk postmenopausal women another risk-management option with fewer of the side effects associated with tamoxifen, but individual patients must weigh the potential risks and benefits of using either drug for their own situations. Factors such as the patient's level of risk for developing invasive breast cancer, other existing medical conditions and medical risks and the degree of potential benefit should be a part of each patient's discussions with her doctor and a part of her ultimate decision to use or not to use available drugs to reduce the risk for developing invasive breast cancer.

Sources:

"Initial Results of the Study of Tamoxifen and Raloxifene (STAR) Released: Osteoporosis Drug Raloxifene Shown to be as Effective as Tamoxifen in Preventing Invasive Breast Cancer, NIH News Release," U.S. Department of Health and Human Services, NIH News, NCI, www.cancer.gov

"The Study of Tamoxifen and Raloxifene (STAR): Questions and Answers," NCI News, STAR Questions and Answers, www.cancer.gov