Hypofractionated WBI plus IOERT-boost in early stage breast cancer (HIOB): Updated results of a prospective trial

Purpose: To assess the role of an intraoperative electron boost (IOERT) in combination with hypofractionated whole breast irradiation (WBI) in terms of inbreast tumor control and cosmetic outcome. Methods: Starting in Jan 2011, a prospective multi-center single arm trial is conducted by the ISIORT. Patients receive an IOERT boost of 10 Gy ( Dmax 11.1 Gy) followed by a WBI of 40.5 Gy in 15 fractions (2.7 Gy single dose). 5-year inbreast- recurrence rates will be analyzed in 3 different age groups (35–40y, 41-50y, > 50y) and tested against the respective best published results from randomized prospective trials by the use of a sequential probability ratio test (SPRT). Acute reactions are assessed by CTC-scoring, late reactions according to LENT-SOMA criteria. Cosmesis is evaluated by a 5-point-Scoring System (vanLimbergen,double evaluation) starting prior to WBI on the basis of repeated photodocumentation in standardized positions. Results:As of Nov 2013, within seven active institutions 426 patients have beenrecruited, 336 of them already in follow-up. Patient and tumor characteristics are summarized in Table 1. For IOERT, the median energy chosen was 7 MeV (range 4- 12) with median tube diameters of 5 cm (4 - 8) and mean prescription depths of 19.4 mm (6.5 SD), resulting in mean D90 volumes of 18 ml. Perioperatively, no major complications were observed. Four weeks after the end of WBI and 336 evaluated patients, 108 (32 %) showed no reactions (CTC 0), 208 (62%) presented with faint (CTC 1) and 20 (6 %) with moderate to brisk erythema (CTC 2), respectively. G0-I late reactions (LENT-SOMA) occurred in a mean frequency of 93 %, 98% and 99% after 4-5 months, 1 and 2 years follow-up, respectively.Cosmesis was assessed postoperatively by patients themselves (subjective) and doctors (objective). Baseline appearance was first assessed after wound healing prior to WBI and scored as sufficient (excellent and good) in 85%/69% of 352 subjective/301 objective evaluations. Respective results at 4-5 months, one and twoyears post RT were 86%/71% of 279/227, 88%/77% of 173 / 75 and 88%/ 74% of 41/31 ratings. At a median follow-up period of 8.2 months (range 0.7 – 28.5), two patients weremetastasized, no in-breast recurrence was noted. Conclusion:Tolerance of a combined IOERT / hypofractionated WBI regimen is excellent, acute reactions moderate and late reactions insignificant in short-term assessment. With regard to postoperative appearance, early cosmetic results are not impaired. Both tumor control and cosmetic outcome have to be evaluated on longterm follow-up.