Accelerated partial-breast irradiation with the intrabeam intraoperative radiotherapy system.

Abstract

e11569 Background: To evaluate intraoperative accelerated partial breast irradiation (APBI) with the Intrabeam System and access its operation, complications, feasibility, efficacy and cosmesis. The rationale for the evaluation was that local failure after breast conserving surgery (BCS) and total breast radiation usually occurs at the site of the original tumor and therefore delivering radiation directly to the tumor bed should result in better local control. Methods: Starting in 2004, patients over age 50 with invasive ductal carcinoma confirmed by core biopsy were enrolled. Preoperative MRI was used to rule out multifocal disease and ultrasound was used to define margins. Only patients with tumors less than 3.5 cm received intraoperative radiotherapy (IORT). In an effort to achieve adequate surgical margins intraoperative ultrasound was utilized. After resection of the tumor, IORT was delivered to the tumor bed with the Intrabeam System. Results: The procedure has been performed on 94 patients. Eighty-four patients had IORT with the primary surgery, while 10 had IROT during re-exploration of the segmental mastectomy site. Because of final pathology (surgical margins, tumor biology and/or nodal status) 4 patients later had total mastectomy and 18 received total breast irradiation. The IORT serves as the radiation boost when total breast irradiation was done. There have been no serious surgical or radiation complications. Cosmetic results were evaluated by the Harvard criteria and have been good to excellent. To date there have been no local failures. However, the follow-up is not long enough to determine the efficacy of preventing local recurrence. Conclusions: The IORT Intrabeam System is easy to use, versatile, accomplishes excellent cosmesis with few complications, and has great patient acceptance. Further, it is cost effective, and practical for breast APBI in the community setting.