The first head-to-head comparison of the drugs tamoxifen and exemestane in women with advanced breast cancer showed the latter was not only safe, it meant an average of four additional months without any progression of the disease.Exemestane, one of a class of drugs called aromatase inhibitors, is currently approved for women whose cancer progressed while they were taking tamoxifen. Two other aromatase inhibitors are also approved in the United States -- letrozole and anastrazole.
