Neoadjuvant Endocrine Therapy in ER-positive, HER2-negative Early Stage Breast Cancer

The goal of this study is to access whether treatment of early state estrogen-rich breast cancers with neoadjuvant endocrine therapy will result in higher rates of margin negativity on lumpectomy specimen.

Inclusion Criteria: * Pathologically confirmed invasive breast cancer, clinically stage I-II. * Clinically lymph node negative * Eligible for anti-endocrine treatment (per medical oncologist) * Postmenopausal women * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Progesterone receptor negativity * High grade tumor * Synchronous non-breast malignancy * Receiving any other investigational agents that could impact the efficacy of this trial regimen * History of allergic reactions attributed to compounds of similar chemical or biologic composition to Anastrozole, Letrozole, Exemestane, Tamoxifen or other agents used in study * Uncontrolled intercurrent illness * Medical, psychiatric or other condition and/or social situations that would limit compliance with study requirements