Evista for Breast Cancer Prevention?

April 17, 2006 -- The osteoporosis drug Evista (raloxifene) may have a major benefit for postmenopausal women at high risk of breast cancer.

Initial results from a large, national study show that Evista equaled an established breast cancerdrug, tamoxifen, at preventing breast cancer in postmenopausal women at increased risk of breast cancer.

What's more, Evista appeared to carry fewer risks of side effects, with lower rates of uterine cancer and clotting problems seen in women who took Evista instead of tamoxifen.

Those findings come from the STAR (Study of Tamoxifen and Raloxifene) trial, which included nearly 20,000 postmenopausal women -- most of whom were white -- at increased risk of breast cancer.

'Good News'

"This is good news for women," Leslie Ford, MD, told reporters during a teleconference. Ford is the associate director for clinical research at the National Cancer Institute's division of cancer prevention.

Ford says, "We've been able to show that [Evista], a drug that's already in widespread use to prevent and treat osteoporosis in postmenopausal women, has the additional benefit of preventing breast cancer, with fewer serious side effects, virtually no increase in uterine cancer, and fewer blood clots and cataracts, when compared to tamoxifen.

"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," she continues, estimating that 150,000 postmenopausal women per year are diagnosed with breast cancer in the U.S.

"We feel that [Evista] is the winner of this trial," D. Lawrence Wickerham, MD, told reporters during the teleconference. Wickerham is STAR trial's protocol officer and the associate chair of the National Surgical Adjuvent Breast and Bowel Project (NSABP).

Head-to-Head Comparison

The STAR participants agreed to take either 20 milligrams of tamoxifen or 60 milligrams of Evista daily for five years.

Tamoxifen has long been used to help fight breast cancer's return. In 1998, the FDA approved tamoxifen for use by women who hadn't had breast cancerbut were at high risk of developing the disease.

Evista is currently taken by about half a million women in the U.S. to prevent and treat osteoporosis, or thinning of the bones. Researchers had previously observed lower rates of breast cancer in women taking Evista than in the general population.

"The unknown was whether or not in a high-risk population, those same benefits could be determined and were they the same as tamoxifen," Wickerham says.

Breast Cancer Results

The women were followed for almost four years, on average. During that time, the tamoxifen group had 163 invasive breast cancers, compared to 167 in the Evista group.

"We recall that compared to placebo, there's a 50% reduction in the risk of breast cancer, invasive breast cancer development, with tamoxifen," Wickerham says. "So we interpret these data as showing that the ability of [Evista] to reduce the risk of invasive breast cancer is equal to that of tamoxifen."

Those results didn't vary among subgroups of participants, including groups based on age, family history of breast cancer, or previous noninvasive breast conditions, the researchers report.