A drug used to treat osteoporosis is as effective as tamoxifen in reducing breast cancer for postmenopausal women who are at increased risk of the disease. And it does so with fewer of the side effects associated with tamoxifen, according to preliminary results of a seven-year study.

Preliminary data from the multi-center "STAR Study" (the "Study of Tamoxifen and Raloxifene"), which included 83 Utah women who took part through the Huntsman Cancer Institute, was released Monday by the National Cancer Institute and the National Surgical Adjuvant Breast and Bowel Project, a network of cancer researchers.

The study found both drugs cut the risk of developing invasive breast cancer in half. But researchers found women who took raloxifene had 36 percent fewer uterine cancers (a very rare but serious side effect of tamoxifen) and 29 perfect fewer blood clots than those taking tamoxifen. Both drugs increase a woman's risk of blood clots compared to those who take neither drug.

"It's clear that we feel raloxifene has been the winner of this trial," Dr. D. Lawrence Wickerham, NSABP associate chairman and STAR protocol officer, said during a teleconference with reporters Monday afternoon.

"We think this gives women a real choice when addressing two of the leading causes of mortality and morbidity as they age — breast cancer and hip fracture," said Dr. Leslie Ford, associate director of clinical research at the NCI.

Prevention studies are extremely important, said oncologist Dr. John Ward, HCI principal investigator for the study and professor of medicine at the University of Utah. He treats women who have breast cancer and is committed to prevention as a better long-term strategy, he said.

This year, about 212,000 women, most of them past menopause, will be diagnosed with breast cancer. More than 40,000 will die of the disease. For the study, women were randomly assigned to receive one or the other of the two medicines, with a placebo version of the other to be sure that neither doctor nor patient could tell who was getting which drug.

Tamoxifen is marketed as Nolvadex, raloxifene as Evista. Tamoxifen has been used for 30 years to treat breast cancer patients. In 1998 it was approved as a prevention tool in high-risk, pre- and postmenopausal women. Raloxifene, also taken by pill, got FDA approval in 1997 to prevent osteoporosis in postmenopausal women but is not approved for use by women before menopause.