According to a recent article published in the
Annals of Internal Medicine, the anti-estrogen agents Nolvadex® (tamoxifen) and Evista® (raloxifene) may help reduce the risk of developing hormone receptor-positive breast cancer in patients at high risk. However, it is important for high-risk patients to discuss the risks and benefits of this preventive therapy with their physician.
Patients at a high-risk for developing breast cancer generally include the following characteristics: family history of breast cancer, early age of beginning of menstruation, previous breast biopsy, even if results were benign, and late age at childbirth or no childbirth. Many women at a high risk for developing breast cancer are interested in preventive strategies, so researchers have been evaluating therapeutic regimens that may help to prevent breast cancer in these women. However, it is important to understand long-term side effects that may be caused by preventive measures prior to making a treatment decision.
The United States Preventive Services Task Force (USPSTF), a group of physicians and other healthcare experts that make recommendations about preventive health care, recently reviewed the results of four large clinical trials conducted in the U.S. and Europe to determine the effectiveness of Nolvadex® and Evista® in preventing breast cancer in high-risk women. Nolvadex® and Evista® are agents that block the growth-stimulatory effects of estrogen on cells. Estrogen provides growth stimulatory effects on some types of breast cancer, called hormone receptor-positive breast cancer.
The review included two clinical trials conducted in the U.S. and two conducted in Europe. Each trial involved patients who were treated with either Nolvadex® or Evista® and were directly compared to patients who were taking placebo (inactive substitute). The two clinical trials conducted in Europe did not demonstrate a reduction of risk for developing breast cancer with Nolvadex®. However, the two U.S. clinical trials, one evaluating Nolvadex® and the other evaluating Evista®, both demonstrated significant reductions in the risk of breast cancer. The U.S. trials involved significantly more women and better compliance to treatment than the European trials. In one U.S. trial, the probability of breast cancer occurring in patients taking Nolvadex® was reduced by nearly 50%, compared to women taking placebo. In the second U.S. trial, the probability of breast cancer occurring in patients taking Evista® was reduced by approximately 76%, compared to women taking placebo. The reduction in breast cancer was only seen in hormone receptor-positive breast cancer. Both Nolvadex® and Evista® increased the risk of blood clots and hot flashes and Nolvadex® slightly increased the risk of uterine cancer and stroke. However, all cases of uterine cancer were early-stage and there were no deaths caused by the disease in these trials.
Based on the review of these results, the task force was unable to clearly define who should or who should not be taking Nolvadex® or Evista® to decrease their risk of developing breast cancer. Another large trial (STAR trial), scheduled to be completed in 2006, which compares Nolvadex® to Evista® may help to define recommended guidelines for breast cancer prevention. For women who are at a high risk for developing breast cancer, it is important that they speak with their physician regarding the risks and benefits of preventive therapy.
Reference: Kinsinger L, Harris R, Woolf S, et al. Chemoprevention of breast cancer: a summary of the evidence for the U.S. Preventive Services Task Force.
Annals of Internal Medicine. 2002;137:59-69.