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Public Citizen, National Women’s Health Network Urge FDA to Require Warnings About Risks Associated with Tamoxifen

May 4, 1999

Public Citizen, National Women’s Health Network Urge FDA to
Require Warnings About Risks Associated with Tamoxifen

Breast Cancer Drug Can Cause Endometrial Cancer, Other Serious Disease

    WASHINGTON, D.C. — Public Citizen and the National Women’s Health Network today petitioned the U.S. Food and Drug Administration to require distribution of a patient Medication Guide outlining the risks to healthy women who are prescribed the breast cancer drug tamoxifen as a way to reduce the incidence of breast cancer. The petition also asks that the FDA revise the physician label for the drug.

    “Most women who are prescribed tamoxifen to reduce their risk of getting breast cancer are not fully apprised of the serious health consequences — such as endometrial cancer or blood clots — that may result,” said Dr. Sidney Wolfe, director of Public Citizen’s Health Research Group. “We believe the current FDA-approved label falls woefully short of providing the clear and accurate information women need to make this life-and-death decision.”

    The petition urges the FDA to published two separate patient guides for tamoxifen (which is sold under the name Nolvadex) — one for the treatment of breast cancer and one for the reduction in incidence of breast cancer. This would prevent patients’ confusion over what information is relevant to them. These guides would include clinical studies, indications and usage, contraindications, precautions and adverse reactions. A revised physician label should separate the two main conditions for which the drug is used, better enabling physicians to interpret the risks and benefits.

    In the only completed clinical trial of tamoxifen’s ability to reduce the incidence of breast cancer, 13,000 women at high risk of invasive breast cancer were followed for a median time of 4.2 years. Half of them took tamoxifen and half took a placebo. In the tamoxifen group, 2.2 percent developed breast cancer compared to 4.3 percent in the placebo group. However, the number of deaths from breast cancer, as well as deaths from all causes, were the same in the two groups.
    “Nothing less than the future health of many women is at stake,” said Cindy Pearson, Director of the National Women’s Health Network. “Women need to know that although they might have a slightly smaller chance of getting breast cancer by using tamoxifen, that benefit might be completely offset by the risk of contracting another deadly disease because of the drug. Unless these risks and benefits are clearly and fully stated, decisions become guesswork rather than rational choices.”

    No one knows if the drug prevented breast cancer from occurring or if the cancers were delayed and appeared later. The study was too short to know if longer exposure to tamoxifen would cause other types of cancer to develop or whether the cancer rates might increase after women stopped taking the drug. Two European trials showed no difference in the number of breast cancer cases between women who took tamoxifen and those who got a placebo.

    Although tamoxifen produced a reduction of 2.9 cases of breast cancer per 1,000 women per year in the U.S. study, it also increased by 2.8 cases per 1,000 women the number of life-threatening adverse events such as uterine cancer, blood clots and stroke. Tamoxifen is a known cancer-causing agent that increases a woman’s chance of developing cancer of endometrium, or lining of the uterus.