ESTRO 2024 - Abstract Book

S1851

Clinical - Mixed sites, palliation

ESTRO 2024

1 Faculty of Medicine and University Hospital Cologne, Department of Radiation Oncology, Cyberknife and Radiotherapy, Cologne, Germany. 2 Olivia Newton-John Cancer Wellness & Research Centre, Austin Health, Department of Radiation Oncology, Melbourne, Australia. 3 University Hospitals Aachen Bonn Cologne Dusseldorf, Center for Integrated Oncology (CIO), Cologne, Germany. 4 Medical Center, Faculty of Medicine, University of Freiburg, Department of Radiation Oncology, Freiburg, Germany. 5 University of Leipzig Medical Center, Department of Radiation Oncology, Leipzig, Germany. 6 University Hospital Erlangen, Department of Radiation Oncology, Erlangen, Germany. 7 University Medical Center of the Johannes Gutenberg University, Department of Radiation Oncology, Mainz, Germany. 8 Jena University Hospital, Department of Radiotherapy and Radiation Oncology, Jena, Germany. 9 Jena University Hospital, Interdisciplinary Center for Clinical Research, Clinician Scientist Program, Jena, Germany. 10 Jena University Hospital, Clinician Scientist Program OrganAge, Jena, Germany. 11 Pius Hospital Oldenburg, University Medicine Oldenburg, Department of Radiation Oncology and Radiotherapy, Oldenburg, Germany. 12 Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, Department of Radiation Oncology, Berlin, Germany. 13 University Medical Hospital, Hamburg Eppendorf, Department of Radiation Oncology, Hamburg, Germany. 14 Outpatient Center of the University Medical Hospital Hamburg-Eppendorf, Department of Radiotherapy and Radiation Oncology, Hamburg, Germany. 15 University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany. 16 University Hospital Tübingen, Department of Radiation Oncology, Tübingen, Germany. 17 University Hospital Dusseldorf, Medical Faculty, Heinrich-Heine-University Dusseldorf, Department of Radiation Oncology, Düsseldorf, Germany. 18 Klinikum rechts der Isar, Technical University Munich, Department of Radiation Oncology, Munich, Germany. 19 German Cancer Consortium (DKTK), Partner site Munich, Munich, Germany. 20 German Cancer Consortium (DKTK), Partner site Munich, Heidelberg, Germany. 21 Medical Faculty, University of Cologne, Institute of Medical Statistics and Computational Biology, Cologne, Germany. 22 University Hospital Bonn, Department of Radiation Oncology, Bonn, Germany. 23 University Hospital Bonn, Institute of Experimental Oncology, Bonn, Germany. 24 University Hospitals Aachen Bonn Cologne Düsseldorf, Center for Integrated Oncology (CIO), Bonn, Germany Improving treatment response to ICI remains a challenge1. Preclinical studies and preliminary research suggest that combining radiotherapy (RT) with ICI may enhance immunogenic responses, including abscopal effects (AbE). AbE represent the regression of tumour lesions outside the irradiation field induced by RT. The mechanism is not fully understood but is likely linked to RT-induced immunogenic cell death and immune system activation. The exact incidence and impact of AbE on oncological outcomes is unclear. This multi-centre study among 8 centres in Germany aimed to determine the occurrence of AbE after RT in patients with disease progression during ICI and to assess its impact on patient outcomes. The study seeks to identify relevant markers enhancing AbE and the response to RT-ICI, with the ultimate goal of developing individualised RT-ICI treatment plans with (re-)activation of the immune system. Purpose/Objective:

Material/Methods:

In this multi-centre study, patients with solid tumours who received combined RT-ICI treatment between 2015 and 2021 were included for analysis. Patients had to have progressive disease under ICI treatment and RT to progressive or symptomatic sites but at least one non-irradiated lesion (NIL) outside the 10% isodose line. For NIL measurement and AbE calculation, cross sectional imaging (MRI, CT, PET/CT) before and after RT was required. Main exclusion