Hypofractionation with simultaneous integrated boost for early breast cancer: Results of the German multicenter phase II trial (ARO-2010-01)

Purpose. To evaluate the feasibility of hypofractionation with SIB in all settings in Germany to prepare a multicenter treatment comparison. Methods. Eligible patients had histopathologically confirmed breast cancer operated by BCS. Patients received WBI 40.0 Gy in 16 fractions of 2.5 Gy. A SIB with 0.5 Gy per fraction was administered to the tumor bed, thereby giving 48.0 Gy in 16 fractions to the boost-PTV sparing heart, LAD, lung, contralateral breast. The primary study objective was feasibility, administration of specified dose in 16 fractions within 22-29 days with adherence to certain dose constraints (heart; LAD; contralateral breast); secondary endpoints were toxicity, QoL. Results. 151 patients were recruited from 7 institutions between 07/11-10/12. 10 patients met exclusion criteria prior to irradiation. All but two patients (99 %) received the prescribed dose in the PTVs. Adherence to dose constraints and time limits was achieved in 89 % (95 % CI 82 % to 93 %). 11 AE were reported in 10 patients; five related to concurrent endocrine therapy. Two of the AEs were related to radiotherapy: grade 3 hot flushes in two cases. QoL remained unchanged. Conclusion. Hypofractionation with a SIB is feasible and was well tolerated in this study.