ESTRO 2025 - Abstract Book

S1716

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

3662

Digital Poster Abscopal effects in malignant melanoma treated with radiotherapy and immune checkpoint inhibition: analysis of a large observational multicenter study Simone Ferdinandus 1,2 , Alexander Rühle 3,4 , Allison Lamrani 5 , Charlotte Schmitter 5 , Justus Kaufmann 6 , Matthias Mäurer 7,8 , Georg Wurschi 9,10 , Ping Jiang 11 , Felix Ehret 12,13 , Andrea Baehr 14 , Annika Hardt 15 , Raphael Bodensohn 16,17 , Lukas Käsmann 16 , Maria Waltenberger 18,19,20 , Davide Scafa 21 , Julian P. Layer 21,22 , Esther Troost 23,24,25 , Sally Abdelhaleem 24,23 , Danny Jazmati 26 , Cindy Franklin 27,2 , Sebastian Neppl 1 , Anna Hagemeier 28 , Maike Trommer 1,2,29 1 Department of Radiation Oncology, Cyberknife and Radiotherapy, Faculty of Medicine and University Hospital Cologne, Cologne, Germany. 2 Center for Integrated Oncology Aachen Bonn Cologne Duesseldorf (CIO), Faculty of Medicine and University Hospital Cologne, Cologne, Germany. 3 Department of Radiation Oncology, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany. 4 Department of Radiation Oncology, University of Leipzig Medical Center, Leipzig, Germany. 5 Department of Radiation Oncology, University Hospital Erlangen, Erlangen, Germany. 6 Department of Radiation Oncology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany. 7 Department of Radiotherapy and Radiation Oncology, Jena University Hospital, Jena, Germany. 8 Clinician Scientist Program OrganAge, Jena University Hospital, Jena, Germany. 9 Department of Radiation Oncology, Jena University Hospital, Jena, Germany. 10 Clinician Scientist Program, Interdisciplinary Center for Clinical Research (IZKF), Jena University Hospital, Jena, Germany. 11 Clinic for Radiation Oncology and Radiotherapy, Lüdenscheid Clinic, Lüdenscheid, Germany. 12 Department of Radiation Oncology, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany. 13 German Cancer Consortium (DKTK), partner site Berlin, a partnership between DKFZ and Charité – Universitätsmedizin Berlin, Berlin, Germany. 14 Department of Radiation Oncology, University Medical Hospital, Hamburg-Eppendorf, Hamburg, Germany. 15 Department of Radiotherapy and Radiation Oncology, Outpatient Center of the University Medical Hospital Hamburg-Eppendorf, Hamburg, Germany. 16 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany. 17 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 18 Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. 19 German Cancer Consortium (DKTK), partner site Munich, Munich, Germany. 20 German Cancer Research Center, (DKFZ), Heidelberg, Germany. 21 Department of Radiation Oncology, University Hospital Bonn, Bonn, Germany. 22 Institute of Experimental Oncology, University Hospital Bonn, Bonn, Germany. 23 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 24 OncoRay- National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, and Helmholtz-Zentrum Dresden-Rossendorf; Institute of Radiooncology - OncoRay Helnholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. 25 National Center for Tumor Diseases (NCT/UCC); German Cancer Research Center (DKFZ) and Helholtz-Zentrum Dresden-Rossendorf (HZDR), Medizinische Fakultät and University, Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 26 Department of Radiation Oncology, University Hospital Dusseldorf, Medical Faculty, Heinrich-Heine-University Dusseldorf, Duesseldorf, Germany. 27 Department of Dermatology and Venereology, Faculty of Medicine and University Hospital Cologne, Cologne, Germany. 28 Institute of Medical Statistics and Computational Biology, Medical Faculty and University Hospital, Cologne, Germany. 29 Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany Purpose/Objective: Abscopal effect (AbE) is the regression of non-irradiated metastatic lesions (NILs) following radiotherapy (RT). Its induction is relevant in malignant melanoma (MM) with progressive disease (PD) under immune checkpoint inhibition (ICI). Even though MM is strongly immunogenic, primary/secondary resistance to immunotherapy remains a challenge. In this study, we assessed the actual incidence of AbE in progressive MM patients by evaluating the effect on non-irradiated lesions (NILs) when RT of metastatic lesions was offered.