Many older women now have a new option to lower their risk for developing breast cancer.

Yesterday, the U.S. Food and Drug Administration approved the drug raloxifene to reduce breast cancer risk in two groups of postmenopausal women: those with the bone-thinning condition osteoporosis and those at high risk for invasive breast cancer.

More than 500,000 women in the United States already take the drug, whose brand name is Evista, manufactured by Indianapolis-based Eli Lilly. The FDA approved its use years ago to prevent or treat osteoporosis in postmenopausal women.

In a statement yesterday, Dr. Steven Galson, director of the FDA's Center for Drug Evaluation and Research, said the expanded use of Evista "provides an important new option for women at heightened risk of breast cancer."

"Because Evista can cause serious side effects, the benefits and risks of taking Evista should be carefully evaluated," he said. "Women should talk with their health care provider about whether the drug is right for them."

Dr. Lawrence Wickerham, chief of medical genetics and cancer prevention at Allegheny General Hospital's breast cancer center, called the announcement "extraordinarily good news for postmenopausal women at increased risk for future breast cancer."

He is also associate chairman of the Pittsburgh-based National Surgical Adjuvant Breast and Bowel Project, which coordinated a major study, known as STAR, on raloxifene and tamoxifen, the only other drug approved to reduce the risk of breast cancer.

If enough women take raloxifene, "we may see a further decline in breast cancers around the country and the world," he said.

After tamoxifen was approved for reducing the risk of breast cancer nearly a decade ago, no significant increase in use of that drug occurred, said Dr. Victor Vogel, co-director of the biochemoprevention program at the University of Pittsburgh Cancer Institute.

"Hopefully, raloxifene won't have the same fate," Dr. Vogel said, adding that research indicates the drug is safer.

Dr. Vogel, who has been a Lilly consultant, was protocol chairman, and Dr. Wickerham protocol officer, of the "Study of Tamoxifen and Raloxifene," or STAR, one of the largest breast cancer prevention trials ever conducted. The study, which received support from the federal government and from AstraZeneca and Lilly, involved more than 19,000 post-menopausal women known to be at high risk for developing breast cancer.

STAR results released last year found that raloxifene was just as effective as tamoxifen in reducing the risk of breast cancer but had a lower risk of blood clots and cataracts.

In its announcement yesterday, the FDA noted that raloxifene can cause serious side effects, including blood clots in the legs and death due to stroke. Other potential side effects include hot flashes, leg cramps, swelling of the legs and feet, flu-like symptoms, joint pain and sweating.

The FDA said women with current or prior blood clots in the legs, lungs, or eyes should not take raloxifene. It also should not be taken by premenopausal women and women who are or may become pregnant. In addition, Evista should not be taken with cholestyramine, a drug used to lower cholesterol levels, or estrogens.

Dr. Vogel said that for many women, the benefits of taking raloxifene outweigh the risks. But time will tell if significant numbers of women elect to take the drug, he said.

"They may say, 'I don't have cancer and I'm not going to do this,' " he said.

Tamoxifen is still the drug of choice for women who have not gone through menopause and have a high breast cancer risk. Raloxifene's breast cancer prevention effects have not been studied in younger women.

George Farra, a principal at Woodley Farra Manion Portfolio Management, a research-based investment management firm in Indianapolis, called the expanded use of raloxifene a "nice add-on" for Lilly.

The company is especially known for mental health drugs such as Zyprexa and Prozac, but hopes to develop a wider array of drugs, Mr. Farra said. Yesterday's approval is a step in that direction, he said.