“…The first attempt at such a study was a retrospective analysis [3]of data derived from randomized clinical trials of therapy in patients with breast cancer [29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41]; data that was collected prospectively. In the National Surgical Adjuvant Breast Project (NSABP) trial B13 study, women with estrogen receptor-positive, node-negative breast cancer received tamoxifen or placebo.…”