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Arimidex Better Than Tamoxifen Long Term

New Option for Some Women With Early Breast Cancer

WebMD Health News

Dec. 11, 2002 (San Antonio, Texas) -- Results of a long-term study show the relatively new drug Arimidex appears to work better than the standard medicine tamoxifen in fighting early breast cancer in postmenopausal women. The findings confirm previous, shorter-term results.

After hearing the findings, doctors attending the 25th Annual San Antonio Breast Cancer Symposium on Wednesday agreed that women with early-stage breast cancer should be told about both options so they can help decide which treatment is best for them.

About three in five women with breast cancer have tumors that are fueled by estrogen, making anti-hormone therapy a cornerstone of treatment to prevent recurrences and improve disease-free survival. For over two decades, doctors have been using tamoxifen, which prevents estrogen from getting into cancer cells, to slow tumor growth.

At last year's Symposium, researchers reported three-year results that showed Arimidex increased disease-free survival better than tamoxifen in early breast cancer. Arimidex is a member of a relatively new class of drugs -- aromatase inhibitors -- that works by slashing the body's production of estrogen.

This compelled many of the nation's 750,000 breast cancer patients who are candidates for anti-hormone therapy to barrage their doctors with calls asking for the novel drugs. And many predicted the standard of practice would change.

That didn't happen. Instead, an expert panel in May said tamoxifen should remain the treatment of choice. The chief reason: A lack of long-term data on the safety and effectiveness of Arimidex, says Eric Winer, MD, head of the expert panel convened by the American Society of Clinical Oncology (ACOG) and a cancer doctor at the Dana-Farber Cancer Institute in Boston.

But the new data, which represents an average of four years of experience with the drug, could change all that.

The study compared Arimidex with tamoxifen in about 9,000 postmenopausal women with early breast cancer. After a median of 47 months of treatment and 54 months of follow-up, 11% of women with hormone-sensitive tumors who took Arimidex suffered relapses or died, compared with 13% of such women who took tamoxifen.

This means that women taking Arimidex are 18% less likely to suffer a recurrence of their disease compared with women taking tamoxifen, says study head Aman Buzdar, MD, an oncologist at the University of Texas M.D. Anderson Cancer Center in Houston.

"Compared with placebo, tamoxifen reduces the risk of recurrence by about 50%. Compared with tamoxifen, Arimidex reduces that risk another 20%. That's a 70% reduction in relative risk," says Buzdar.

As for side effects, unlike tamoxifen, Arimidex is not associated with an increase in the risk of uterine cancer or dangerous blood clots. But patients taking Arimidex are more susceptible to bone fractures than those taking tamoxifen, an indication that the new drug accelerates bone loss. A bone-building supplement could prevent many aromatase inhibitor-related fractures, Buzdar says.

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