Bone Drug Effective in Preventing Invasive Breast Cancer

CINCINNATI—University of Cincinnati (UC) cancer specialists report encouraging results in a trial of an osteoporosis drug for the prevention of breast cancer.

Comparing the osteoporosis drug raloxifene (Evista) with the widely used breast cancer medication tamoxifen (Nolvadex), the researchers found not only that the drugs were equally effective, but that raloxifene also had fewer side effects.

Led by Elizabeth Shaughnessy, MD, PhD, an assistant professor of surgery at UC, the Cincinnati research was part of a national study of nearly 20,000 postmenopausal women, one of the largest breast cancer prevention studies ever conducted in the United States.

Known as the STAR study (the Study of Tamoxifen and Raloxifene), the research was part of the National Surgical Adjuvant Breast and Bowel Project, funded by the National Cancer Institute (NCI). 

About 12 percent of the Ohio patients were treated in Cincinnati. Patients were recruited through University, Christ and Good Samaritan hospitals.

“Tamoxifen has been used for more than 30 years to treat patients with breast cancer, but it also has known—though rare—serious side effects,” says Dr. Shaughnessy. “We wanted to know how raloxifene compares to tamoxifen in reducing breast cancer in postmenopausal women at high risk for the disease.”

Participants, all of whom were postmenopausal and considered at increased risk for breast cancer, were randomly assigned to receive either raloxifene or tamoxifen daily for five years.  Risk was determined on the basis of their age, family history of breast cancer, personal medical history, and age of first menstrual cycle and first live childbirth.

“Our data showed that raloxifene was just as effective as tamoxifen for reducing breast cancer risk in postmenopausal women,” explains Dr. Shaughnessy. “In fact, both drugs reduced the risk for developing breast cancer by 50 percent.

“Raloxifene, however, did so with fewer serious side effects—including uterine cancers, blood clots and cataracts,” she adds.

Researchers found that the women who took raloxifene daily over four years experienced 36 percent fewer uterine cancers and 29 percent fewer blood clots than those who took tamoxifen.

“Although no drugs are without side effects, tamoxifen and raloxifene are vital options for women who are at increased risk of breast cancer and want to take action,” said Leslie Ford, MD, associate director for clinical research in the NCI’s Division of Cancer Prevention.  “For many women, raloxifene’s benefits will outweigh its risks in a way that tamoxifen’s benefits do not.”

The NCI estimates that half a million postmenopausal women are already taking raloxifene to prevent or treat osteoporosis.

AstraZeneca Pharmaceuticals and Eli Lilly and Company, maker of tamoxifen and raloxifene, respectively, provided drugs and matching placebos for the trial at no charge to participants. Eli Lilly also gave support to cover recruitment costs and to help local investigators conduct the study.

More than 214,000 women will be diagnosed with breast cancer in 2006, according to the American Cancer Society, and 19 percent will die from it.

For more information on the STAR trial results, visit www.cancer.gov/star.