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Evista for Breast Cancer Prevention?

Study: Osteoporosis Drug Evista Trumps Tamoxifen in High-Risk Women

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.

Side Effects

Uterine cancer and clotting problems were less common with Evista than with tamoxifen.

The tamoxifen group had 36 cases of uterine cancer, compared with 23 with Evista. Pulmonary embolism (in which a blood clot travels to the lungs) and deep vein thrombosis (in which a blood clot develops in the deep veins) were both markedly less common in the Evista group, the researchers report.

Cataracts and cataract surgery were also less common with Evista, the study shows. Stroke and heart disease risks didn't differ between the two groups.

Tamoxifen showed reduced risk of noninvasive breast cancers (lobular carcinoma in situ and ductal carcinoma in situ), but there was no risk reduction for those conditions with Evista.

Reviewing the Options

"The results released today show [Evista] is as effective as tamoxifen at reducing the risk of invasive breast cancer with a better safety profile. But there's an important caveat," says Len Lichtenfeld, MD, the American Cancer Society's deputy chief medical officer, in an ACS statement.

The "caveat" Lichtenfeld refers to is the higher rate of noninvasive breast cancer in STAR participants taking Evista.

"The outcome of the study is not as clear-cut as we might have hoped for," Lichtenfeld states. "It will take some time for experts to review the data to determine which of the two treatments is preferable.

"For now it will be very important for women at increased risk of breast cancer to make an informed decision with the advice of their physician as to which approach is best for them. It is also important to note that while both drugs can prevent many breast cancers, neither has been shown to reduce the risk of death due to the disease," Lichtenfeld says.

Responding to the ACS statement, Wickerham told reporters that the clinical implication of the noninvasive breast cancer findings "remains to be seen," but that doesn't change his view of the overall results.

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