Endocrine Response in Women With Invasive Lobular Breast Cancer

OBJECTIVES Primary 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). Secondary * To evaluate ER protein expression in ILC tissues at baseline and following neoadjuvant endocrine therapy. * To evaluate PR protein expression in ILC tissues at baseline and following neo-adjuvant endocrine therapy. * To evaluate ER-related and ILC-specific candidate gene mRNA expression in ILC tissues at baseline and following neoadjuvant endocrine therapy in an effort to identify biomarkers of endocrine response and putative drivers of endocrine resistance in ILC. * To evaluate associations between changes in Ki67 in ILC tissues following neoadjuvant endocrine therapy with ER and PR protein expression, or ER and candidate gene mRNA expression at baseline and post-treatment. Exploratory * To evaluate DNA methylation in ILC tissues at baseline and following neo-adjuvant endocrine therapy. * To evaluate associations between germline and somatic DNA sequence variants with changes in Ki67 in ILC tissues following neo-adjuvant endocrine therapy. * To evaluate the activity of signaling pathways in ILC tissues by immunohistochemical or other protein analyses, such as histone modifications, at baseline and following neo-adjuvant endocrine therapy.