Dosimetric comparison of 192Ir high-dose-rate brachytherapy vs. 50 kV x-rays as techniques for breast intraoperative radiation therapy: Conceptual development of image-guided intraoperative brachytherapy using a multilumen balloon applicator and in-room CT imaging

A Novel Form of Breast Intraoperative Radiation Therapy With CT-Guided High-Dose-Rate Brachytherapy: Results of a Prospective Phase 1 Clinical Trial

“…The approach tested in the current trial delivers a prescription dose of 12.5 Gy to the PTV_eval, which is substantially higher than the 5-7 Gy delivered to 1 cm from the applicator in the TARGIT trial [16,20]. The TARGIT and ELIOT trials provide evidence that suggests IORT may be an acceptable option in the treatment of early-stage breast cancer, but there are drawbacks to those radiotherapy delivery techniques.…”

“…This dose was selected to replicate the dose delivered to the surface of the applicator using low energy photons and, at 1cm from the surface, corresponds to an equivalent dose in 2 Gy fractions of 28.1 Gy (assuming α/β = 10 for acute effects) [20]. The prescribed dose was calculated in an attempt to increase the dose at 1cm depth compared to the alternative low-energy kV IORT technique [16], while maintaining an acceptable dose at the applicator surface [20]. The investigators chose this dose-selection strategy empirically due to concerns regarding risk of fat necrosis from high dose volumes in breast tissue.…”

“…Despite these relatively favorable clinical results, there are several well-recognized limitations to available forms of IORT. Most important are the lack of intraoperative imaging (which can be used for catheter placement confirmation, target delineation, and simulate/optimize radiotherapy delivery) and the poor dosimetry resultant from the physical limitations of low-energy photons [19,20]. We sought to improve upon these technical limitations by devising a novel form of IORT at our institution that incorporates threedimensional treatment planning, image-guidance, and higher prescription dose.…”

“…Compared to other forms of IORT, HDR brachytherapy allows for superior target volume coverage and a higher prescription dose delivered to the adjacent breast tissue without excessive balloon surface dose [20]. A multichannel brachytherapy balloon allows computerized optimization of the dose on the CT dataset so that the dose delivered to critical structures (skin, ribs, heart, and chest wall) is within tolerance while not sacrificing coverage of the target volume [20]. To demonstrate the feasibility M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 and safety of CT-HDR-IORT in partial breast irradiation, we conducted a phase I trial of this novel approach.…”

“…The CT images provide the ability to evaluate applicator placement and facilitate customized treatment planning [21] . Compared to other forms of IORT, HDR brachytherapy allows for superior target volume coverage and a higher prescription dose delivered to the adjacent breast tissue without excessive balloon surface dose [20]. A multichannel brachytherapy balloon allows computerized optimization of the dose on the CT dataset so that the dose delivered to critical structures (skin, ribs, heart, and chest wall) is within tolerance while not sacrificing coverage of the target volume [20].…”