IOERT as anticipated tumor bed boost during breast conserving surgery after neoadjuvant chemotherapy in LABC – Results of a retrospective analysis after 5-year follow-up.

Purpose: Ipsilateral breast tumor recurrence rates (IBTR) are reported to be increased in patients with locally advanced breast cancer (LABC) after breast conservation (BC) following primary systemic treatment (PST). Aim of this study was to evaluate locoregional tumor control rates in patients with LABC who were treated with preoperative chemotherapy followed by breast conserving surgery and intraoperative radiotherapy with electrons (IOERT) preceeding whole breast irradiation (WBI). Methods and Metrials: From 2002 to 2007, 83 patients with clinical stage II or III breast cancer were enrolled. Patients received 3 to 6 cycles of anthracyclin/taxane containing preoperative chemotherapy. All patients had breast conserving surgery with sentinel node biopsy and axillary lymph node dissection and received intraoperative radiotherapy with 9 Gy to the 90% reference isodose as anticipated tumor bed boost. WBI was performed after surgery for all patients with single fractional doses of 1.7 – 1.8 Gy (5x/week) to total doses of 51 - 57 Gy. Results: Two patients refused WBI, leaving 81 patients for further analysis. Pathologic complete response was achieved in 14/81 (17%) patients. After a medianfollow-up of 59 months (range 3 – 115), two IBTR, both in the former index quadrant and two regional recurrences (RR) were observed, corresponding to a local control rate (LCR) of 98.5% and a locoregional control rate (LRCR) 94.8%. Metastases free survival (FFM), disease free survival (DFS), disease specific survival (DSS), and overall survival (OS) rates amounted 86.8%, 80.7%, 89.2% and 86.4%, respectively. Conclusions: Likewise to its potential in multimodal adjuvant regimen, IOERT as boost modality during breast conserving surgery is an effective tool for the prevention of IBTR in LABC following neoadjuvant chemotherapy