Neoadjuvant anastrozole or tamoxifen for premenopausal breast cancer: Ki67 expression data from the STAGE study

501^ Background: The study of tamoxifen or arimidex, combined with goserelin acetate, to compare efficacy and safety (STAGE) study recently reported a greater best overall tumor response rate (BORR) for anastrozole 1 mg/day plus goserelin 3.6 mg/month (A+G) versus tamoxifen 20 mg/day plus goserelin 3.6 mg/month (T+G) during 24 weeks of pre-operative breast cancer treatment. We report the preplanned exploratory analysis of Ki67 expression. Methods: STAGE is the first phase III, randomized, double-blind, parallel-group, multicenter study which enrolled premenopausal Japanese women with estrogen receptor-positive (ER+), HER2-, operable breast cancer. Tumor response was measured by caliper and MRI or CT. Ki67 indices (%), ER and progesterone receptor (PgR) Allred scores were determined from samples obtained at baseline (Day 0) and surgery (Wk 24). Ki67 ratio from baseline to Wk 24 was calculated; the estimate of reduction ratio between groups was compared by ANCOVA. A post hoc analysis explored any correlatio...