The study is being conducted to determine whether neoadjuvant endocrine therapy with fulvestrant or the combination of anastrozole and fulvestrant, is better than anastrozole when given before surgery to shrink the cancer and stop it from growing. Anastrozole inhibits tumor growth by reducing the levels of estrogen and has been approved by the Food and Drug Administration (FDA) of the United States for use after surgery for postmenopausal women with estrogen receptor positive breast cancer. It is also considered a standard of care to give anastrozole for a few months before surgery to shrink the tumor. Fulvestrant inhibits tumor cell growth by reducing the levels of estrogen receptor in the tumor cell. It is not approved by the FDA for use in women with early stage breast cancer before or after surgery, but is approved by the FDA for patients with advanced (Stage 4) estrogen receptor positive breast cancer that has spread to other parts of the body.