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According to results published in the Journal of the American Medical Association (JAMA), Nolvadex® (tamoxifen) and Evista® (raloxifene) are equally effective at preventing invasive breast cancer in high-risk postmenopausal women. Evista may be less effective at reducing the risk of noninvasive breast cancers (such as DCIS or LCIS), but was also linked with fewer serious side effects such as blood clots and cataracts.

Breast cancer causes roughly 40,000 deaths annually in the U.S. alone. 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.

Some postmenopausal women at a high risk of developing breast cancer can be treated with the anti-estrogen agent Nolvadex. In high-risk women, Nolvadex reduces the risk of breast cancer by approximately 50%. This reduced risk of breast cancer, however, is accompanied by an increased risk of conditions such as endometrial (uterine) cancer and blood clots.

Evista is an agent that also reduces the stimulatory effects of estrogen on cancer growth. It is 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.

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Researchers conducted a clinical trial, referred to as the STAR trial (The NSABP Study of Tamoxifen and Raloxifen [STAR] P-2 Trial), to directly compare Evista to Nolvadex in the prevention of breast cancer in women who were considered at high risk of developing the disease. A woman’s risk of breast cancer was estimated based on family history of breast cancer, personal medical history, age, age at first menstrual period, and age at first live birth. The trial enrolled over 19,000 women who have been followed for just under four years.

  • Evista and Nolvadex were similarly effective in reducing the risk of developing invasive breast cancer.
  • There was a trend toward a reduced risk of uterine cancer among women treated with Evista.
  • Women treated with Evista had a 30% lower risk of developing blood clots compared to women treated with Nolvadex.
  • Women treated with Evista had an approximately 21% lower risk of developing cataracts compared to women treated with Nolvadex.
  • Women treated with Evista had more cases of noninvasive breast cancer (lobular carcinoma in situ or ductal carcinoma in situ) than women treated with Nolvadex.

The researchers conclude that Evista is as effective as Nolvadex in reducing the risk of invasive breast cancer in high-risk postmenopausal women, and carries a lower risk of blood clots and cataracts.

Evista is not currently approved for prevention or treatment of breast cancer.

Reference: Vogel VG, Costantino JP, Wickerham DL et al. Effects of Tamoxifen vs Raloxifene on the Risk of Developing Invasive Breast Cancer and Other Disease Outcomes. Journal of the American Medical Association. 2006;295:(doi:10.1001/jama.295.23.joc60074).