FLT PET in Measuring Treatment Response in Patients With Newly Diagnosed Estrogen Receptor-Positive, HER2-Negative Stage I-III Breast Cancer

PRIMARY OBJECTIVES: I. Measure the effect of a short course of endocrine therapy on primary breast cancer metabolism and proliferation by measuring changes in serial FLT PET measures pre and post a short course of endocrine therapy. SECONDARY OBJECTIVES: I. Compare changes in imaging measures to tissue measures of response, in particular antigen identified by proliferation-related Ki-67 antigen (Ki-67), in the pre-therapy biopsy versus the post-therapy surgical specimen. II. Correlate imaging measures to measures of gene expression from pre and post therapy assays to determine if there are molecular changes associated with early response to therapy. OUTLINE: Patients undergo FLT PET at baseline and 1-6 weeks after the start of treatment.