ESTRO 2025 - Abstract Book

S1197

Clinical – Lower GI

ESTRO 2025

2229

Poster Discussion Dose-effect relationship on response rates and toxicity in total neoadjuvant therapy for locally advanced rectal cancer – A multicenter analysis Georg W Wurschi 1,2 , Miriam Kesselmeier 3 , Melanie Schneider 4 , Jan-Niklas Becker 5 , Bernd Frerker 6 , Samuel Vorbach 7 , Felix Ehret 8,9 , Markus Diefenhardt 10,11 , Fabian Schunn 12 , Maria-Elena von Gruben 13 , Marcel Büttner 14,15,16 , Maike Trommer 17 , Julian Hlouschek 18 , Kynann Aninditha 19 , Daphne Schepers-von Ohlen 20 , Justus Kaufmann 21 , Alina Depardon 22 , Hai Minh Ha 23 , Simon Trommer 24 , Christopher Kessler 25 , Adrianna Cieslak 26 , Alexander Fabian 27 , Mathias Sonnhoff 28 , Alexander Rühle 29,30,31 , Klaus Pietschmann 1,2 1 Department of Radiotherapy and Radiation Oncology, Jena University Hospital, Jena, Germany. 2 Comprehensive Cancer Center Central Germany (CCCG), Campus Jena, Jena, Germany. 3 Institute of Medical Statistics, Computer and Data Sciences (IMSID), Jena University Hospital – Friedrich Schiller University Jena, Jena, Germany. 4 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 5 Department of Radiotherapy, Hannover Medical School, Hannover, Germany. 6 Department of Radiotherapy and Radiation Oncology, Rostock University Medical Center, Rostock, Germany. 7 Department of Radiation Oncology, Medical University of Innsbruck, Innsbruck, Austria. 8 Department of Radiation Oncology, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany. 9 German Cancer Consortium (DKTK), partner site Berlin, a partnership between DKFZ and Charité – Universitätsmedizin Berlin, Berlin, Germany. 10 Department of Radiotherapy and Oncology, University Hospital, Goethe University Frankfurt, Frankfurt, Germany. 11 Frankfurt Cancer Institute (FCI), University Hospital, Goethe University Frankfurt, Frankfurt, Germany. 12 Department of Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany. 13 Department of Radiotherapy and Radiation Oncology, University Hospital Hamburg-Eppendorf, Hamburg, Germany. 14 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 15 German Cancer Consortium (DKTK), Partner Site Tübingen, Tübingen, Germany. 16 German Cancer Research Center, DKFZ, Heidelberg, Germany. 17 Department of Radiation Oncology, Cyberknife and Radiotherapy, Faculty of Medicine and University Hospital Cologne, Cologne, Germany. 18 Department of Radiotherapy, West German Cancer Center, University Hospital Essen, Essen, Germany. 19 Department of Radiooncology, Klinikum Stuttgart, Stuttgart, Germany. 20 Department of Radiotherapy, University Medical Center Schleswig-Holstein/Lübeck, Lübeck, Germany. 21 Department of Radiooncology, University Medical Center of the Johannes-Gutenberg-University Mainz, Mainz, Germany. 22 Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany. 23 Department of Radiation Oncology, Otto von Guericke Universität Magdeburg, Magdeburg, Germany. 24 Department for Radiotherapy, University Hospital Halle, Halle, Germany. 25 Department of Radiation Oncology, Technical University of Munich (TUM), School of Medicine and Klinikum rechts der Isar, Munich, Germany. 26 Department of Radiation Oncology, University Medicine Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany. 27 Department of Radiation Oncology, University Hospital Schleswig-Holstein Campus Kiel, Kiel, Germany. 28 Center for Radiotherapy and Radiation Oncology, Bremen, Bremen, Germany. 29 Department of Radiation Oncology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK), partner site DKTK-Freiburg, Freiburg, Germany. 30 Department of Radiation Oncology, University Medical Center Leipzig, Leipzig, Germany. 31 Comprehensive Cancer Center Central Germany (CCCG), Campus Leipzig, Leipzig, Germany Purpose/Objective: Total neoadjuvant therapy (TNT) improves local control and complete response (CR) rates in locally advanced rectal cancer (LARC) [1-3]. CR is a key predictor of tumor control. The impact of cumulative doses and TNT duration on CR and toxicity remains unclear and was analyzed in the multicenter “TNTox” study (DRKS00033000), conducted by the Young DEGRO. Material/Methods: LARC patients (UICC stage II/III) treated with TNT, including only consolidation chemotherapy, between 2015 and 2023 across 21 centers in Germany and Austria were included. We standardized oxaliplatin and 5-fluorouracil doses to