Tamoxifen May Not Prevent Breast Cancer
Brainard, Jeffrey, Science News
U.S. researchers sparked a transatlantic debate this spring when they announced that the drug tamoxifen can prevent women from developing breast cancer. Researchers in Britain responded that longer studies were necessary to justify that conclusion.
Now, two teams of European researchers offer some support for those critics. In the July 11 Lancet, both groups report preliminary findings that indicate tamoxifen--a widely prescribed medication for limiting breast cancer recurrence--provides no significant protective effect.
Like the U.S. researchers, teams in England and Italy examined whether the drug reduces the number of new cases of cancer among healthy women with no previous breast cancer but who were, for a variety of reasons, at high risk of contracting the disease.
Neither study found a significant difference in cancer incidence between women who took an inactive substance, or placebo, and those who received tamoxifen. In contrast, the U.S. Breast Cancer Prevention Trial had found that among participants diagnosed with invasive breast cancer, almost twice as many were taking the placebo as tamoxifen (SN: 4/11/98, p. 228).
Citing statistical shortcomings in their own data, the European investigators stop short of dismissing tamoxifen's preventive effects and instead call for further research. The British team, led by Trevor Powles of the Royal Marsden NHS Trust in Surrey, England, reports a chance of about 1 in 10 that their study erred in failing to observe the effect reported by the U.S. team. The finding in the Italian Tamoxifen Prevention Study, by researchers at the European Institute of Oncology in Milan, appears less powerful still.
The U.S. team calculated the odds at 1 in 10,000 that its results were due to chance alone. Barnett Kramer of the National Cancer Institute (NCI) in Bethesda, Md., which sponsored the U.S. study, argues that this trial was the most accurate because of its large size--13,388 women participated. …