ESTRO 2022 - Abstract Book

S747

Abstract book

ESTRO 2022

Conclusion The volume of maxilla irradiated with high dose values was relevant for the ORN development in our ACC patients’ cohort. These results were in line with the previously published data obtained with a different radiobiological model. Our finding might be helpful to prevent ORN risk in patients receiving CIRT.

Proffered Papers: Highlights of Proffered Papers - Latest Clinical Trials

OC-0829 Acute toxicity after loco regional breast radiation therapy in the randomized DBCG SKAGEN trial 1

M.L. Milo 1 , T. Lörincz 1 , M.H. Nielsen 2 , C. Kamby 3 , T. Bechmann 4 , S. Al-Rawi 5 , L.W. Matthiessen 6 , M. Krause 7 , A. Schreiber 8 , I. Mjaaland 9 , U. Kasti 10 , E.S. Brix 11 , P. kedzierawski 12 , T. Marinko 13 , C. kirkove 14 , J. Overgaard 15 , B.V. Offersen 15 1 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 2 Odense University Hospital, Department of Oncology, Odense, Denmark; 3 Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 4 Vejle Hospital, Department of Oncology, Vejle, Denmark; 5 Naestved Hospital, Department of Oncology, Naestved, Denmark; 6 Herlev Universiyt Hospital, Department of Oncology, Herlev, Denmark; 7 University Hospital and Faculty of Medicine Carl Gustav Carus, Department of Radiation Oncology and OncoRay, Heidelberg, Germany; 8 Dresen Hospital, Department of Radiotherapy, Dresen, Germany; 9 Stavanger University Hospital, Department of Oncology, Stavanger, Norway; 10 Sørlandet Hospital, Department of Oncology, Kristiansand, Norway; 11 University of North Norway, Department of Oncology, Tromsø, Norway; 12 Holycross Cancer Center, Department of Radiotherapy, Kielce, Poland; 13 Institute of Oncology Ljubljana, Department of Radiotherapy, Ljubljana, Slovenia; 14 Cliniques Universitaires St-Luc, Department of Oncology, Brussel, Belgium; 15 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark Purpose or Objective Background: In the past, poor outcome after hypofractionated radiation therapy (RT) in breast cancer patients (pts) was observed. Thus, in Denmark, normofractionation with 50Gy/25fr was standard for early breast cancer (BC) RT since 1982. In 2014, moderately hypofractionated RT became standard for pts treated with whole breast RT based on early results from the Danish Breast Cancer Group (DBCG) Hypo trial. The DBCG Skagen trial 1 was then initiated to evaluate the risks and gains following 50Gy/25fr versus moderately hypofractionated 40Gy/15fr loco-regional RT of BC pts with indication for loco-regional RT (LR-RT). The primary endpoint was 3-year arm lymph edema. In this study, we report evaluation of acute toxicity, a secondary outcome of the trial. Materials and Methods Method: In this international, multi-center, randomized trial, pts operated for early BC, pT1-3, pN0-N3, M0 with an indication for LR-RT were randomly assigned 50Gy/25fr (standard) versus 40Gy/15fr (experimental). Acute toxicities were graded using the CTCAE 4.0 and the RTOG/EORTC criteria at baseline, three and five weeks after start of RT. Hereafter, evaluations were made every 2 weeks as long as there were acute morbidities above baseline level. The maximum grading is reported here. Each center was requested to report acute morbidities in 40 consecutive pts. Results Results: From 2015 to 2021, 511 pts from six countries were evaluated for acute toxicity. In total, 259 pts were randomized to 50Gy/25fr and 252 pts to 40Gy/15fr No acute grade 4-5 toxicities were observed. For both randomization arms, grade 3 toxicity was observed in only 10% of the pts. The most common grade 2 toxicities were dermatitis 52% (50Gy/25fr) versus 27% (40Gy15fr) and fatigue 18% (50Gy/25fr) versus 19% (40Gy15fr), respectively. The most common grade 1 toxicities were dermatitis, pruritus and fatigue. Conclusion Conclusion: In general, the frequency and severity of acute toxicities were low for pts treated with LR-RT regardless the randomization arm. Thus, moderately hypofractionated RT did not raise any safety concerns. A more detailed analysis of