ESTRO 2025 - Abstract Book

S1795

Clinical – Upper GI

ESTRO 2025

2191

Poster Discussion Outcome of magnetic resonance guided stereotactic body radiotherapy for hepatocellular carcinoma - an R IDEAL stage IIb trial Marcel Büttner 1 , Laura Uder 1 , Marcel Nachbar 2 , Monica Lo Russo 1,3 , David Mönnich 2 , Moritz Schneider 2 , Jessica Boldt 1 , Sarah Kübler 1 , Sabrina Baumeister 1 , Pavlos Missios 4 , Michael Bitzer 4,3 , Silvio Nadalin 5 , Rüdiger Hoffmann 6 , Konstantin Nikolaou 6,3 , Daniela Thorwarth 2,3 , Maximilian Niyazi 1,3 , Daniel Zips 7 , Cihan Gani 1,3 , Simon Böke 1,3 1 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 2 Section for Biomedical Physics, Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 3 German Cancer Consortium (DKTK), partner site Tübingen, and German Cancer Research Center (DKFZ), Heidelberg, Germany. 4 Department of Internal Medicine I, University Hospital Tübingen, Tübingen, Germany. 5 Department of General and Transplant Surgery, University Hospital Tübingen, Tübingen, Germany. 6 Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany. 7 Department of Radiation Oncology, Charité, Universitätsmedizin Berlin, Berlin, Germany Purpose/Objective: Evidence is growing for the benefit of stereotactic body radiotherapy (SBRT) in the treatment of hepatocellular carcinoma (HCC). Magnetic resonance guided SBRT (MRgSBRT) might prove beneficial due its superior soft tissue contrast. The present analysis reports on all patients treated with HCC with markerless MRgSBRT on a 1.5 T MR linear accelerator (MRL). Material/Methods: All consecutive patients treated within a prospective basket trial (NCT04172753) with fraction doses ≥ 5 Gy, receiving MRgSBRT between August 2019 and July 2024 have been included in the analysis. The analysis assesses local control of the treated lesion (LC), intrahepatic control (IHC), overall survival (OS), progression free survival (PFS) and patient reported outcomes as well as toxicity, scored using Common Toxicity Criteria Version 5. Results: A total of 54 HCC lesions in 47 patients receiving online adaptive MRgSBRT have been analyzed. Indication for MRgSBRT was based on discussion in multidisciplinary tumor board and most patients had previous or subsequent interventional therapy (microwave ablation and/or transarterial chemoembolization). Median age was 75 (range 52 to 81) years. Indication was primary treatment in 24 patients (51.1 %), oligo-progression in 9 patients (19.1) and as a bridge to transplant in 14 patients (29.8%). A median of 35 (range of 25 to 50) Gy was applied in 5 fractions (range 3 to 6). Median FU was 14 (range 1 to 50) months. LC and IHC was 94,5 % and 63 %. Mean OS and PFS was 18.8 and 13.7 months, respectively. For the group of patients receiving treatment with BED > 100 Gy (n= 10), no local failures were observed up to a medium FU of 20.5 months. Of the patients treated for bridging 8 patients (57 %) proceeded to receive liver transplantation. No toxicity beyond CTC grade > 2 has been observed. Conclusion: Non-invasive, online adapted MRgSBRT for HCC in this prospective cohort of patients proved to be well tolerable with encouraging oncologic outcome for definitive treatment and bridging.

Keywords: HCC, MRgRT, SBRT