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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...

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."

If you and your doctor conclude you are at increased risk and you are not at risk for blood clots or uterine cancer, both drugs are good breast cancer prevention options, Hortobagyi says. If you are at risk for these problems, Evista is the better choice, he says.

All things being equal, some women may want to take tamoxifen because it is slightly more effective, the experts say.

On the other hand, postmenopausal women with thinning bones might want to consider Evista because it "offers two benefits in one," Lippman says.

The study only included postmenopausal women, but as a treatment for breast cancer, tamoxifen has a proven track record in premenopausal women as well, Hortobagyi says. Evista is only approved for use after menopause, so its safety and effectiveness in premenopausal women is unknown, he says.

High-risk premenopausal women who have had a hysterectomy -- and therefore a "close to nonexistent" risk of uterine cancer -- and who have no history of blood clots may want to talk to their doctor about taking tamoxifen, he says.

Both drugs cost about $140 a month or $8,400 for five years of treatment. In comparison, treating one case of early breast cancer can easily cost $50,000 to $120,000, according to Hortobagyi.


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