Endocrine Response in Women With Invasive Lobular Breast Cancer

RATIONALE: Currently, adjuvant endocrine therapy often follows a "one-size-fits- all" approach, with most premenopausal women receiving tamoxifen, and most postmenopausal receiving aromatase inhibitor therapy. In current clinical practice, patients with invasive lobular carcinoma are treated no differently than patients with invasive ductal carcinoma based on the void of information specific to patients with this tumor type. Identification of a biological signal of tamoxifen and/or AI-resistance and/or fulvestrant-sensitivity in ILC patients would have dramatic implications for the future management of this breast cancer subtype. PURPOSE: To study whether fulvestrant is more effective than anastrozole or tamoxifen in reducing Ki67 in ILC and whether that Ki67 reduction will correlate with alterations in expression of ER and ER-regulated genes. Differential Ki67 effect in this study will serve as a surrogate for outcome of ILC patients on endocrine therapy. Primary Objective: To determine the change from baseline to post-treatment Ki67 values in ER-positive, HER2-negative ILC tissue derived from postmenopausal women awaiting definitive surgery or further neoadjuvant treatment who are randomized to 21-24 days of neoadjuvant endocrine treatments with fulvestrant (two 250 mg IM injections given on day 1), anastrozole (1mg given orally daily), or tamoxifen (20mg given orally daily).