T. Hassinger1, K. Rea1, A. Schroen1, D. Brenin1, A. Berger2, B. Libby3, T. Showalter3, S. Showalter1 1University Of Virginia,Department Of Surgery, Division Of Surgical Oncology,Charlottesville, VIRGINIA, USA 2Thomas Jefferson University,Department Of Surgery,Philadelphia, PENNSYLVANIA, USA 3University Of Virginia,Department Of Radiation Oncology,Charlottesville, VIRGINIA, USA
Introduction: Intraoperative radiation therapy (IORT) is an increasingly popular approach to breast conservation. A drawback to conventional breast IORT (CB-IORT) is the lack of CT imaging. We pioneered a novel method of IORT that incorporates customized, CT-based treatment planning and high-dose-rate (HDR) brachytherapy; Precision Breast IORT (PB-IORT). Our aim is to report on the unique utility of CT imaging in PB-IORT, both intraoperatively and in dosimetric planning for the first 84 patients treated in two prospective trials.
Methods: We retrospectively reviewed the first 84 patients who participated in prospective clinical trials of PB-IORT. The first 28 were enrolled in the phase I trial, and the subsequent 56 are enrolled in the ongoing phase II trial. All patients underwent lumpectomy, multicatheter balloon placement, intraoperative CT scan, and HDR brachytherapy treatment delivery to 12.5 Gy to 1 cm from the balloon surface. This report focuses on the intraoperative CT findings that led to clinical changes and the use of the CT to make adjustments to the dosimetry.
Results: After initial intraoperative CT, 18 patients (21.4%) had findings that prompted surgical adjustment of the balloon applicator to eradicate large air cavities and/or improve tissue conformity between the balloon and the breast tissue before planning and delivering IORT. In 1 patient, an additional intraoperative CT scan was performed to localize a biopsy clip and aid in excision to negative margin. In 66 patients (78.6%), the dosimetry plan was modified based on intraoperative CT findings in order to sculpt the radiation dose off of the chest, ribs, or skin, with 31 patients (36.9%) adjusted for one reason and 35 patients (41.7%) adjusted for more than one reason.
Conclusion: Intraoperative CT findings were used in a majority of patients treated with PB-IORT in order to enhance tissue conformity between the breast tissue and the balloon and to sculpt the radiation dose away from normal tissues. CT imaging is not available in CB-IORT. These findings suggest the potential for clinical superiority of our technique employing intraoperative CT given its allowance for patient-specific alterations in both the area and dose of HDR brachytherapy.
