RESULTS: HISTOLOGY ELECTRONIC (NON-ISOTOPIC) HIGH DOSE RATE BRACHYTHERAPY (EHDRB): DESIGN, CHARACTERIZATION AND PILOT ANIMAL TRIAL OF A NOVEL METHOD OF ACCELERATED PARTIAL BREAST IRRADIATION

This study was an in vivo test to demonstrate delivery of therapeutic dose in therapeutic time of EHDRB, a novel approach that delivers HDR ionizing radiation to the tumor bed using a fully electronic system. This was made possible through the recent development of a disposable, micro-miniature x-ray source.. X-rays of 40-50 keV are produced at the tip of a cooled, flexible, disposable probe otherwise closely resembling current remote afterloading units, with dose rates comparable to HDR Ir-192. Control variables are source energy level (penetration depth), dose rate and dwell position, for interstitial or intracavitary use, with greatly reduced shielding and other safety concerns. A prototype balloon-based partial breast irradiation system has undergone physical testing and characterization; this report details the device performance in a Nubian milk goat mammary model. Five of the animals entered into a Good Laboratory Practices (GLP) study received 10 fractions of 3.4 Gy at 1 cm depth over five days. Device performance, balloon conformance and electromechanical safety were excellent. Procedure tolerance was good and no acute radiation or thermal complications were noted, grossly or in histologic post-mortem studies. Our prototype to deliver EHDRB performed safely and delivered the expected dose to mammary tissue as predicted from preclinical studies. Study funded by Xoft microTube Inc.