Stereotactic Image-Guided Neoadjuvant Ablative Radiation Then Lumpectomy

Inclusion Criteria: * Age ≥ 50 years and postmenopausal * Tumor size \< 3cm on pre-treatment imaging * Any grade of disease, estrogen receptor (ER) positive * Unicentric/unifocal disease * Invasive ductal carcinoma or other favorable subtypes of epithelial breast malignancy (lobular, medullary, papillary, colloid, mucinous, or tubular) . * Clinically node-negative (based upon pre-treatment physical examination and/or axillary ultrasound). * Surgical expectation that a \> 2mm margin can be obtained. * Lesion is 1 cm or greater from the skin surface. * Able to have surgery within 14-20 days of radiation therapy. * Able to lie comfortably in the prone position with arms raised above the head for extended periods of time. Exclusion Criteria: * Previous RT to the same breast * Evidence of suspicious diffuse microcalcifications in the breast prior to the start of radiation. * Local metastatic spread into ipsilateral axilla and/or supraclavicular region and/or neck nodes and/or internal mammary nodes diagnosed on clinical examination or any imaging assessment (unless such sites can be confirmed as negative following biopsy) * Distant metastases * Involvement of contralateral axillary, supraclavicular, infraclavicular or internal mammary nodes (unless there is histologic confirmation that these nodes are negative) * Prior non-hormonal therapy or radiation therapy for the current breast cancer * Patients with Paget's disease of the nipple. * Skin involvement, regardless of tumor si…