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Tamoxifen as Prevention Questioned

Popular Breast Cancer Drug May Not Lengthen Life for Most

Tamoxifen vs. Raloxifene

Breast cancer prevention researcher D. Lawrence Wickerham, MD, of the National Surgical Adjuvant Breast and Bowel Project (NSABP), tells WebMD that very few women at the low end of the high-risk scale are taking tamoxifen for prevention.

Wickerham and colleagues recently reported findings from a long-awaited study comparing tamoxifen to raloxifene for breast cancer prevention in postmenopausal women.

He tells WebMD that the Study of Tamoxifen and Raloxifene (STAR) showed both drugs worked equally well, reducing breast cancers to about half of what would have been expected. But raloxifene was found to have a better safety profile, with a lower risk of causing uterine cancer, blood clots, and cataracts.

Raloxifene, which is manufactured by Eli Lilly and sold under the brand name Evista, is widely prescribed for osteoporosis, but it has not yet been approved for breast cancer prevention.

Fewer Side Effects?

"We viewed raloxifene as the winner, not because it was more effective, but because it was as effective as tamoxifen with fewer side effects," Wickerham says. "Raloxifene may prove to be the drug that makes prevention treatment both practical and effective."

But breast cancer specialist William J. Gradishar, MD, is not yet convinced. In an editorial evaluating the STAR results, Gradishar noted that the difference in side effects between the two drugs was slight and that tamoxifen seemed to prevent more noninvasive breast cancers than raloxifene.

"Although media coverage of the early release of data from the STAR trial suggests a clear winner in raloxifene, the data from clinical end points and patient-reported symptoms suggest a less clear conclusion," Gradishar wrote.

Reluctance to Use Drug

The Northwestern University oncology professor tells WebMD that women and their primary care physicians have been slow to embrace tamoxifen for cancer prevention. He does not see them flocking to raloxifene once it is approved for this use.

"We are asking women to take a costly drug with potential side effects every day for five years to lower their risk for a cancer than may or may not occur," he says. "Not many women have been willing to do that."

And large numbers probably won't, he says, until better breast cancer prevention drugs with fewer side effects become available or there are better ways of identifying the women who are likely to get breast cancer.

If you're considering using one of these drugs, talk to your physician about what your breast cancer risk is.

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