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Breast Cancer Health Center

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Tamoxifen, Evista Prevent Breast Cancer

Study Shows Tamoxifen Is a Little More Effective, but Evista May Have Less Risk

Tamoxifen vs. Evista continued...

The new findings suggest that several years after treatment, which lasts about five years, tamoxifen is substantially better than raloxifene at preventing breast cancer.

About two years after treatment ended, tamoxifen reduced the risk of invasive breast cancer by 50%, while Evista cut risks by 38%.

Put another way, Evista was 76% as effective as tamoxifen, says Wickerham, who serves as a consultant to makers of both drugs.

Evista was about 78% as effective as tamoxifen at preventing noninvasive breast cancers (lobular carcinoma in situ and ductal carcinoma in situ).

But women who took Evista "continued to have substantially fewer of the serious side effects, including uterine cancers, clotting problems, and cataracts, that seem to be barriers to tamoxifen use," he says.

There were 2.25 cases of uterine cancer per 1,000 women treated with tamoxifen vs. 1.23 per 1,000 among women treated with Evista. There were 3.30 blood clot events per 1,000 women treated with tamoxifen vs. 2.47 per 1,000 among women treated with Evista.

"The absolute risk of these problems for any given woman is quite low, regardless of treatment," says M.D. Anderson's Scott Lippman, MD.

There was no difference in death rates among the two groups. Neither of the drugs has been shown to extend lives in high-risk women.

Who Is Considered a High-Risk Patient?

So which drug is better for which women? Both drugs are only for women at high risk, doctors stress.

In the study, women were considered to be at high risk if their risk of developing breast cancer over the next five years was 1.67% based on a simple formula called the Gail model that takes into account age, family history, and other factors. By definition, anyone over age 60 was at high risk.

But Hortobagyi says he probably wouldn't give the drugs to a woman in her 60s who is otherwise healthy based on age alone. "It's a discussion each woman needs to have with her doctor. The more risk factors, the greater she will benefit."

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