Breast Cancer Prevention Trial (BCPT): Tamoxifen as Prevention Therapy for Breast Cancer

In Spring 1998, the National Cancer Institute announced positive results from the Breast Cancer Prevention Trial (BCPT), a clinical trial that studied tamoxifen as a prevention therapy for those at high risk for breast cancer.

The BCPT, part of the National Surgical Adjuvant Breast and Bowel Project (NSABP), began in April 1992 to determine whether the non-steroidal anti-estrogen tamoxifen could reduce the incidence of breast cancer in women who were at high risk for development of the disease. Only women who were at increased risk for developing breast cancer participated in the study. They were chosen based on their breast cancer risk as determined by a computer calculation that included specific factors.

By September 1997, more than 13,000 women had participated in the study. Data showed the results of tamoxifen treatment to be "highly significant" with a 45 percent reduction in the number of invasive breast cancers seen across all age groups.

The data were then turned over to the Endpoint Review, Safety Monitoring, and Advisory Committee for review of toxicity, adverse side effects, and effectiveness of tamoxifen. This independent committee (whose members are not affiliated with either the NSABP or the BCPT) concluded that the overall benefits of treatment with tamoxifen outweighed the overall risks.

Tamoxifen is one of the most widely prescribed cancer drugs in the world, and has been the focus of research on its actions, benefits, and risks for more than 25 years. The success of its use as preventive therapy for breast cancer is exciting news for both patients and the medical community.

Physicians and researchers caution, however, that, as positive as the BCPT results are, tamoxifen therapy may not be appropriate for all women who are at increased risk for breast cancer.

Before tamoxifen is prescribed, a woman and her physician should take into consideration her age, personal history, and family history. She and her physician should also weigh the benefits and risks of tamoxifen. Having an understanding of the protocols used in the BCPT will also help in making the decision on whether to take tamoxifen as preventive therapy.

The use of tamoxifen is reportedly associated with some infrequent, but potentially life-threatening side effects. Endometrial cancer, pulmonary embolism, and deep vein thrombosis were noted in the BCPT as conditions that may be caused or adversely affected by tamoxifen.

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