Ten-year outcomes after breast-conserving surgery with intraoperative radiotherapy for breast cancer

The purpose of the study was to analyze the 10-year outcomes after breast-conserving surgery with electron-beam intraoperative radiation therapy (IORT) followed by external beam radiotherapy (EBRT) in patients with breast cancer. Material and methods. The study included 905 patients with stage T1-2N0-1M0 breast cancer, who underwent breast-conserving surgery. Group I consisted of 746 patients who received IORT at a single dose of 10 Gy, biologically equivalent to 24.8 in standard fractionation, followed by EBRT at a total dose of 46 ± 8.1 Gy. A combined IORT and EBRT photon-equivalent dose delivered to the tumor bed was 60 Gy. Group II (control group) comprised 159 who received EBRT at a total dose of 40-44 Gy delivered to the remaining breast tissue and electron therapy delivered to the area of postoperative scar (a single 3-4 Gy fraction, 3 days per week, to the total photon-equivalent dose of 15-18 Gy). The combined photon-equivalent dose was 58 Gy. Results. According to RTOG/EORTC toxicity criteria, grade 1 radiation-induced damage was observed in 413 (55.3 %) patients of Group I and in 71 (44.6 %) patients of Group II (р=0.2); grade 2 radiation-induced damage in 76 (10.1%) and 43 (27 %) patients (p=0.0002) and grade 3 in 18 (2.4 %) and 9 (5.7 %) patients, respectively (р=0.1). Late radiation-induced injuries (grade I and 2) were mostly observed in the control group. Local recurrence was diagnosed in 11 (1.47 %) patients of Group I and in 14 (8.8 %) patients of Group II. The 10-year disease-free survival rates were 97.3 ± 1.08 % and 88.96 ± 2.8 % in Group I and Group II patients, respectively (р function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }