Radiation Therapy Before Surgery in Treating Patients With Hormone Receptor Positive, HER2 Negative Breast Cancer

PRIMARY OBJECTIVES: I. To evaluate the change in percent tumor-infiltrating lymphocytes (TIL) as a continuous variable before and after preoperative boost radiotherapy (RT) in hormone receptor (HR)+/human epidermal growth factor receptor2 (HER2)- breast cancers. SECONDARY OBJECTIVES: I. To evaluate the safety of preoperative boost RT administered to patients with HR+/HER2- breast cancer. EXPLORATORY OBJECTIVES: * I. To assess the mechanisms of cell death induced by preoperative boost RT. * II. To assess immunologic and molecular responses to preoperative boost RT. * III. To assess the correlations between immune markers, cell death markers, and their changes during treatment. * IV. To determine if magnetic resonance imaging (MRI) can be used to predict breast tumor response to neoadjuvant radiation. OUTLINE: Patients undergo boost radiation therapy 6-8 days before breast surgery. After surgery, patients continue to receive standard of care radiation therapy. After completion of study treatment, patients are followed up at 6 months.