Peter D Beitsch1, Rakesh R Patel2, John D Lorenzetti3, James C Wurzer4, James C Tucker5, Susan J Laduzinsky6, Morris A Kugler71Dallas Surgical Group, Dallas, TX, USA; 2Valley Medical Oncology Consultants, Pleasanton, CA, USA; 3Breast Specialists, Egg Harbor Township, NJ, USA; 4AtlantiCare Regional Medical Center, Egg Harbor Township, NJ, USA; 5DCH Regional Medical Center – Tuscaloosa, AL, USA; 6Memorial and St Elizabeth’s Cancer Treatment Center, Swansea, IL, USA; 7Southern Illinois Surgical Consultants, Maryville, IL, USAIntroduction: Electronic brachytherapy (EBT) was developed to allow accelerated partial breast irradiation to be performed in a patient procedure room with minimal shielding. This observational, nonrandomized, multicenter study evaluated EBT as a post-surgical adjuvant radiation therapy for early stage breast cancer.Methods: This study included women aged 50 years or more with invasive carcinoma or ductal carcinoma in situ, tumor size ≤3 cm, negative lymph node status, and negative surgical margins. The endpoints were skin and subcutaneous toxicities, efficacy outcomes, cosmetic outcomes, and device performance. In this interim report, 1-month, 6-month, and 1-year follow-up data are available on 68, 59, and 37 patients, respectively.Results: The EBT device performed consistently, delivering the prescribed 34 Gy to all 69 patients (10 fractions/patient). Most adverse events were Grade 1 and included firmness, erythema, breast tenderness, hyperpigmentation, pruritis, field contracture, seroma, rash/desquamation, palpable mass, breast edema, hypopigmentation, telangiectasia, and blistering, which were anticipated. Breast infection occurred in 2 (2.9%) patients. No tumor recurrences were reported. Cosmetic outcomes were excellent or good in 83.9%–100% of evaluable patients at 1 month, 6 months, and 1 year.Conclusion: This observational, nonrandomized, multicenter study demonstrates that this EBT device was reliable and well tolerated as an adjuvant radiation therapy for early stage breast cancer.Keywords: radiation therapy, electronic brachytherapy, breast cancer