TBCRC 037: A Trial of Endocrine Response in Women with Invasive Lobular Breast Cancer (H-43764)

This study is being done to determine the change from baseline to post-treatment Ki67 (a protein that indicates how quickly cancer cells are forming) in hormone receptor positive, HER2-negative invasive lobular breast cancer tissue derived from postmenopausal women awaiting surgery or further neoadjuvant treatment. Participants are randomized to 21-27 days of neoadjuvant endocrine therapy with fulvestrant, anastrozole or tamoxifen.