The Food and Drug Administration has given six-month Priority Review Status for the drug Arimidex in the treatment of early breast cancer in postmenopausal women. This "fast track" status is generally granted for new drugs, or new uses for existing drugs, that "represent a significant improvement in efficacy or safety over existing treatments."

The agency based its decision on the results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) study of over 9,300 women, which indicated that Arimidex may be significantly more effective and have important tolerability benefits compared with the current gold standard, tamoxifen, as an adjuvant treatment in postmenopausal women with early breast cancer.

After an average of 33 month's follow-up, Arimidex monotherapy was found to be more effective in preventing relapse than tamoxifen, with a 17 per cent reduction in risk of breast cancer recurring with Arimidex treatment compared with tamoxifen.

Arimidex was also associated with significantly fewer reports of endometrial cancer when compared with tamoxifen. This finding was supported by a lower incidence of vaginal bleeding and vaginal discharge among Arimidex-treated patients compared to those taking tamoxifen.

Another known risk associated with tamoxifen is thromboembolic events. In the ATAC trial, both the overall incidence of thromboembolic events and that of deep vein thromboses were significantly reduced in the Arimidex group. The incidence of hot flushes and weight gain were also lower.

Conversely, women taking tamoxifen had a lower risk of experiencing musculo-skeletal disorders or the types of fractures common in this age group compared with those taking Arimidex.

SOURCES:
U.S. Food and Drug Administration (http://www.fda.gov)
AstraZeneca International (http://www.astrazeneca.com)