A new "black box" Food and Drug Administration warning on tamoxifen may just make Therese Bevers difficult job a little harder.
Bevers, medical director of the Cancer Prevention Center at the University of Texas M. D. Anderson Cancer Center, spends a great deal of time easing the apprehension many primary care physicians feel over prescribing tamoxifen to their patients who are at high risk for developing breast cancer (see main story). Now shes concerned that the new FDA warning on the label about the risk of developing a rare, aggressive form of uterine cancer may impede her progress.
Documents released by the FDA in June include the revised label, "Dear Doctor" letters, and a new patient insert, all of which are largely aimed at use of the drug for chemoprevention. Although tamoxifen use has long been associated with an elevated risk of developing the most common form of endometrial cancer, which is relatively treatable, recent data indicate a newly recognized increased risk of a more deadly uterine sarcoma. For example, long-term follow-up on 8,306 women with an intact uterus who participated in the BCPT trial show that endometrial cancer was reported in 53 women who took tamoxifen and 17 who were prescribed a placebo, and 4 women who used tamoxifen in the trial developed a uterine sarcoma, while no cases appeared in the placebo group.
The job for Bevers is to put those numbers into perspective. "It translates to less than one-tenth of 1%, and has to be weighed against the serious benefit many women receive in using the agent," she said.
The risk of uterine sarcoma is not "a new issue with tamoxifen," said Joseph Purves, M.D., senior medical director at AstraZeneca Pharmaceuticals, which makes tamoxifen (marketed as Nolvadex). But he wrote the May 15 "Dear Doctor" letter to physicians because "it was important to let them know this information, even though it is such a small risk and the overall risk of developing any uterine cancer has not changed."
News about the warning does not take the bloom off the tamoxifen rose, said Northwestern University researcher Craig Jordan, Ph.D., D.Sc., who helped develop the drug. "It is a very small incidence and only relevant to chemoprevention," he said.
"This is an issue of a rolling horizon," he said. "As information comes to light over time, it is made available, and thats how it should be." But Jordan also stressed that "more than 500,000 women worldwide are alive today because they received tamoxifen as a treatment for breast cancer," and added, "We dont know how many more we can save with widespread use of tamoxifen as a preventative."
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