Evaluation of a Once Per Day Regimen of Accelerated Partial Breast Irradiation for Improved Breast Appearance in Pts w/Low Risk, Hormone Responsive Brst Ca

PRIMARY OBJECTIVES: I. To establish that APBI delivered once per day (APBI QD) for low-risk breast cancer patients results in acceptable patient-reported cosmetic appearance of the breast at 1 year after completion of APBI QD. SECONDARY OBJECTIVES: I. To determine the long-term patient-reported cosmetic appearance of the breast in patients treated with APBI QD. II. To determine the short-term and long-term physician reported cosmetic appearance of the breast in patients treated with APBI QD. III. To determine the acute and late patient-reported radiation toxicity of APBI QD. IV. To determine the acute and late physician-reported radiation toxicity of APBI QD. V. To determine the cancer control outcomes of APBI QD. EXPLORATORY OBJECTIVES: I. To assess the health-related quality of life in patients treated with APBI QD. II. To determine the long-term blinded physician review of cosmetic appearance of the breast in patients treated with APBI. III. To assess dosimetric parameters associated with cosmesis in patients undergoing APBI QD. OUTLINE: Patients undergo APBI QD on consecutive business days for 5 treatments. Patients follow up at 1 month, 6 months, and 1 year post-APBI and then yearly until 5 years post-APBI.