Tamoxifen reduces that risk substantially, according to the clinical trial that led to FDA approval. In this 1,804-patient trial, women first received lumpectomy and radiation therapy, a standard treatment for DCIS, and then were randomly divided into two groups to receive either tamoxifen or a placebo. The study is the latest, but by no means last, in a series of findings from clinical trials exploring the uses of tamoxifen. First studied as a treatment for advanced breast cancer, the drug later moved into studies to treat early breast cancer, and then into primary prevention trials. But even with FDA approval in these three settings, the tamoxifen story is not yet over.
Researchers continue to ask questions about the drug.
The study was not designed to show whether the tamoxifen would reduce breast cancer death rates, however. Some information on mortality may come from the International Breast Cancer Intervention Study, which is comparing tamoxifen to a placebo in 7,000 women at increased risk of the disease. The primary aim of this trial is to compare the incidence of breast cancer in the two groups, but it will also assess mortality, other cancers, cardiovascular disease, and fractures according to Jack Cuzick, Ph.D., of the Imperial Cancer Research Fund, London. He projected all 7000 participants needed would be enrolled by the end of the year. For some investigators, tamoxifen's success in both prevention and treatment studies has set the stage for its use in combination with other agents that may also span these two uses.