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Breast Cancer Health Center

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Tamoxifen Prevents Breast Cancer

WebMD Health News

March 21, 2002 -- Long-awaited preliminary results from the largest ever Nolvadex (tamoxifen) trial are in, and they show what so many had hoped to be true: The drug does, indeed, prevent breast cancer in high-risk healthy women.

The findings were presented March 20 at a European breast cancer conference in Barcelona.

Professor Jack Cuzick, PhD, lead researcher of the International Breast Cancer Intervention Study (IBIS), says that breast cancer incidence was one-third lower in the women taking Nolvadex than in those taking a placebo.

The IBIS trial included 7,000 healthy women. When the researchers included results from nine additional studies that included women who'd already had breast cancer, the protective effect of Nolvadex was even stronger, bringing the reduction in new cancers to 38% and reduction in second cancers in the opposite breast to 46%.

The benefit was seen only for hormone positive, or estrogen-receptor positive, cancers. There was no similar reduction in risk for estrogen-receptor negative cancers. The level of reduction was the same across all age groups, all risk levels, and whether or not a woman was taking hormone replacement therapy.

The benefits are clear, but Nolvadex isn't without side effects. In the IBIS trial, as in previous trials, there was a two- to threefold increase in both uterine cancer and dangerous blood clots in the women taking Nolvadex.

"It is about the same level of risk as that faced by a woman taking hormone replacement therapy," says Cuzick, "and if you are a breast cancer patient taking tamoxifen for treatment it is absolutely essential that you continue the treatment. Tamoxifen is a lifesaver and the single most effective medical treatment for breast cancer. Any risks from tamoxifen used for treatment are far outweighed by the benefits."

What remains to be seen, he says, is whether the benefits outweigh the risks for those women taking Nolvadex to prevent, rather than treat, breast cancer.

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