"Examples of Trials and Understanding Results "

Early results from the largest cancer adjuvant treatment trial ever conducted were recently published.   Arimidex and Tamoxifen Alone or in Combination (ATAC) was an adjuvant breast cancer trial in post-menopausal women.  This was a randomized, double blind trial (neither doctor nor patient know which drug is received), with 3 treatment arms enrolling 9,366 women from 380 centers in 21 countries between 1996 and 2000.  All women received two pills.  Arm A was tamoxifen and arimidex; Arm B tamoxifen and placebo; Arm C arimidex and placebo.  It was sponsored by the ATAC Trialists’ Group, which was funded by a pharmaceutical company.   Only a single, independent statistician was aware of the code to the blinded data as the trial progressed.  Not even the sponsoring pharmaceutical company was aware of the results until they were unblinded.  The results were unblinded on the day it was first presented at the largest annual breast cancer conference in 2001 in San Antonio. Although survival data are still pending, the updated interim results (at average 47 months follow-up) revealed three important findings:  1) Arimidex reduced the number of cancer recurrences (by 14% compared to Tamoxifen);  2)  Arimidex reduced the number of new invasive breast cancers in the opposite breast (by 37% compared to Tamoxifen); and 3) that the toxicity profile of Arimidex is superior to Tamoxifen.  The impact of this trial may displace Tamoxifen, which has been the standard of care for postmenopausal adjuvant treatment of breast cancer for the past 30 years.