For one of the drugs, the government had a stark message Tuesday: Despite headlines trumpeting raloxifene, a new osteoporosis drug, there is no good evidence yet that the medicine truly wards off breast cancer.
But a National Cancer Institute study did find that a related medicine called tamoxifen cuts the chances of breast cancer by a significant 45 percent in certain women. The NCI said Tuesday it is preparing kits to help doctors target just those women whose potential benefit from the pills would outweigh the side effects.
"The message very much is, each woman is different," said Dr. Richard Klausner, NCI's director. "There is no cut-and-dried formula" to say who needs the drug.
A 35-year-old woman whose mother and aunt both had breast cancer and who has undergone biopsies herself for early signs of the disease is a good tamoxifen candidate, said Dr. Norman Wolmark, the Pennsylvania doctor who led the tamoxifen study.
But tamoxifen can cause potentially life-threatening side effects, including uterine cancer and blood clots, and women over 50 were particularly vulnerable, noted Cynthia Pearson of the National Women's Health Network.
For every 1,000 women over 50 who still had a uterus, tamoxifen prevented 20 breast cancers but caused 22 life-threatening complications, she said, concluding that taking tamoxifen may not be a good choice for such women unless they have had a hysterectomy.
The decision isn't based just on breast cancer riskÂ—among other things, doctors must know if a woman has high blood pressure and already is at increased risk of a blood clot.
And Klausner acknowledged that doctors still don't know how long women should take tamoxifen there are other studies that suggest taking it for longer than five years makes tumors that crop up later harder to treat. Nor do they know if tamoxifen is delaying breast cancer's appearance instead of totally preventing it.
"It is a step forward," stressed Klausner, who has been traveling the country to explain the findings to doctors confused about prescribing tamoxifen. But, he cautions, "many questions remain."
Federal researchers announced on April 6 that tamoxifen, which has been used for more than two decades to fight cancer, also is the first drug shown to prevent breast cancer in some women. They cautioned at the time that it was only for women at high risk, but just which women that means has been a source of confusion for doctors and their patients.
By Lauran Neergaard.
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