A Novel Delivery of Accelerated Partial Breast Irradiation Using Intraoperative Brachytherapy Device Placement and Completion of Breast Conservation Therapy Within 10 Days

Abstract

Accelerated partial breast irradiation (APBI) is a treatment option for early stage breast cancer. To improve patient compliance with adjuvant radiotherapy and decrease the total time for completion of breast conservation therapy (BCT), we initiated intraoperative catheter placement and starting brachytherapy within 2 weekdays. From October 2012 to December 2016, 190 patients were prospectively evaluated and registered for intraoperative brachytherapy catheter placement. Inclusion criteria included age ≥ 50 years, estrogen receptor positive invasive carcinoma or ductal carcinoma in-situ, ≤ 2 cm on imaging, and negative surgical margins and sentinel lymph node (SLN) on intraoperative pathology. Target volume was defined as 1 cm of breast tissue beyond the cavity limited to exclude pectoralis, chest wall, and within 5 mm of skin surface. 3D planning was performed on CT images obtained on the weekday after surgery and treatment was initiated on the following weekday. The cumulative incidence of recurrence was estimated considering death as a competing risk. 170 patients (89%) had intraoperative catheter placement. 19 patients were registered but did not have catheter placed due to intraoperative findings (11 positive SLN, 5 extensive disease, 2 failed SLN mapping, 1 no residual disease). One patient had delayed positive SLN on permanent pathology and catheter was used to boost the cavity prior to converting to whole breast radiation. Prescription doses were 34 Gy in 10 BID (57%), 32 Gy in 8 BID (14%), and 21 Gy in 3 daily (29%) fractions. Median age was 67 and 9% were premenopausal. Median tumor size was 0.9 cm, 18% DCIS, and 6% grade 3. BCT was completed in a median of 9 days. Three patients received adjuvant chemotherapy and 64% had adjuvant endocrine therapy. Median follow up is 1.7 years (39% with at least 2 years), and 2-year local recurrence rate is 2%. Intraoperative pathology and brachytherapy catheter placement with initiation of APBI within 2 weekdays allows completion of BCT within 10 consecutive days in select patients with low short-term local recurrence rate. Long term follow up is planned for oncologic and cosmetic outcomes.