The osteoporosis drug raloxifene (Evista) is equivalent to tamoxifen in its ability to I reduce breast cancer risk in high-risk postmenopausal women, and has fewer side effects, according to a recent study.

The Study

The clinical trial, called the Study of Tamoxifen and Raloxifene (STAR), was initiated in 1999 and involves almost 20,000 women, making it one of the largest breast-cancer prevention trials ever conducted.

The participants, all of whom were post menopausal and at a heightened risk for breast cancer, were randomly assigned to receive either 60 milligrams (mg) of raloxifene or 20 mg of tamoxifen daily for approximately four years.

Both drugs reduced the risk of developing invasive breast cancer by approximately 50%, the researchers report. However, the women taking raloxifene had 36% fewer uterine cancers and 29% fewer blood clots than the women taking tamoxifen. The risks of stroke, heart attack and bone fracture were the same in each group. In addition, the study found that, unlike tamoxifen, raloxifene did not increase the risk of developing cataracts.

Good News

"This is good news for women," says Dr. Leslie Ford, associate director for clinical research in the Division of Cancer Prevention at the National Cancer Institute. "'We think that this gives women a real choice for addressing two of the leading causes of morbidity and mortality as they age-breast cancer and fractures."

"We now have two medicines that can be given to high-risk women to decrease their chances of developing breast cancer," explains Dr. B. Jay Brooks, Jr., chairman of hematology/oncology at the Ochsner Clinic Foundation in Baton Rouge, Louisiana. The bottom line, he says, is to make sure women understand that there are options for reducing breast cancer risk.

"We can predict which women are at a high risk for developing the disease and we can do something about that. Not enough women and physicians understand that," Brooks adds.

Tamoxifen Vs Raloxifene: No Clear Answer

The US Food and Drug Administration (FDA) approved tamoxifen in 1998 to reduce the odds of high-risk women getting breast cancer. "This was a major step in our battle against breast cancer. However even with cutting breast cancer risk in half, [tamoxifen] got little use because of the rare but serious side effects that we knew occurred." Ford says.

"Evista is as good as tamoxifen in preventing invasive breast cancer and it has fewer side effects. I think we'll see a shift over to the use of Evista," Brooks says.

Dr. Lawrence Wickerham, associate chairman of the National Surgical and Adjuvant Breast and Bowel Project and STAR protocol officer, concurs. "N7e believe that raloxifene is the winner of this trial," he says.

However, despite these positive results, raloxifene was not effective against in situ (noninvasive) breast cancers. Tamoxifen had previously been shown to reduce the incidence of these types of breast cancers by half.

"There's an important caveat," says Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "Taking away the increased risk of uterine cancer and blood clots from tamoxifen comes at a price. The outcome of the study is not as clear-cut as we might have hoped for" he adds.

In addition, tamoxifen is the only drug currently approved for breast cancer risk-reduction in premenopausal women-and it will probably stay that way, according to Dr. Victor Vogel, STAR protocol chairman. "We anticipate that if [Eli] Lilly gets approval [for raloxifene], the indication will only be for postmenopausal women, so tamoxifen will remain the drug of choice for reducing risk in premenopausal women," he says.

Trial participants who were taking raloxifene will continue to receive the drug until they have completed five years of treatment. Women in the trial who were taking tamoxifen can continue or can choose to get raloxifene instead.

Raloxifene is currently approved only to prevent or treat osteoporosis. An estimated 500,000 postmenopausal American women are taking the drug for this use.

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