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Breast Cancer Health Center

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Tamoxifen as Prevention Questioned

Popular Breast Cancer Drug May Not Lengthen Life for Most

All in the Numbers continued...

Meanwhile, tamoxifen use is associated with an increased risk for uterine cancer. Tamoxifen is also associated with increased risk for serious blood clots that can be life-threatening, and for cataracts.

The researchers concluded it would take a breast cancer risk of greater than 3% to derive a potential mortality benefit from tamoxifen.

The model did show a mortality benefit for tamoxifen users at all levels of risk if the women had had hysterectomies. The increased risk of uterine cancer from using tamoxifen does not exist for these women.

"The projected benefits of tamoxifen for women at or near the threshold risk for breast cancer of 1.67% are very small or nonexistent," Melnikow and colleagues conclude in the Sept. 1 issue of the American Cancer Society journal Cancer.

Melnikow tells WebMD that women with a five-year breast cancer risk of less than 2.5% or 3% should probably not take tamoxifen, especially if they have not had hysterectomies.

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."

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