WASHINGTON — Women who are at high risk for breast cancer can cut their chances of developing the disease by about half, at least over the short term, by taking the drug tamoxifen.
That finding is the main conclusion of the Breast Cancer Prevention Trial, a huge federally funded study that was halted last week when the benefit of the drug became obvious to scientists and officials overseeing it.
The drug, however, has some serious side effects and the study does not indicate that it is appropriate for women who do not fall into one of the groups known to have a high breast cancer risk.
Details of the study will be presented today at a news conference in Washington.
The study enrolled about 13,000 women from the United States and Canada. It was scheduled to last at least a year longer.
Tamoxifen is not without its own risks or side effects. While it reduces a high-risk woman's chances of breast cancer, it also raises threefold her risk for uterine cancer. It also increases the risk of developing blood clots, including dangerous ones that migrate to the lungs.
A scientist familiar with the study results warned against any conclusion that tamoxifen is of benefit to all, or even most, women.
Physicians, patients, and women's health advocates will have to review the study before making clinical recommendations. However, "the first caveat has to be that [any recommendation] has to be restricted to high-risk women who would have been eligible for this trial," scientists said.
Other people familiar with the study said any recommendation would probably include a warning that tamoxifen should not be taken for more than five years.