Xoft® Intraoperative Radiotherapy (IORT) for Patients With Early-Stage Breast Cancer

Inclusion Criteria: * T1 or T2 invasive carcinoma of the breast undergoing breast conserving surgery * Clinically lymph node negative and Memorial Sloan Kettering nomogram estimates 20% or less risk of positive sentinel node * Tumors 2.5 cm or less in size (clinical preoperative staging) * Estrogen receptor positive tumors (≥10%) * Her2 negative/not over-expressed * Patients 50 years of age or greater Exclusion Criteria: * Prior malignancy not in remission * Active collagen vascular disease requiring active cytotoxic or immunotherapy * Psychiatric or mental condition which would preclude informed consent * Prior thoracic radiation which overlaps with IORT field * Pregnant patients * Patients \<50 years * Risk of positive sentinel lymph node \>20% based on nomogram estimates * Known lymph node metastases (i.e. clinically node positive) * Patients with invasive lobular carcinoma * Patients with pure DCIS * Known multifocal or multicentric tumor * Patients requiring neoadjuvant chemotherapy * Patients requiring or choosing mastectomy with or without reconstruction * Technical contraindications to IORT dose delivery including skin to balloon distance \<7 mm * Medical contraindication to IORT, radiation or breast conservation