S1122
Clinical – Upper GI
ESTRO 2026
treatment was in 5 cases. The 1-year overall survival was 88.3%. The 1-year local control was 96.0% and local recurrence occurred in one case. In recurrence case, PRV interfered with the PTV, and the prescribed dose was 35 Gy. No Grade 2 or higher acute and late gastrointestinal toxicities were observed, and the gastrointestinal dose constraints were within limits for both the treatment plan and each treatment session. Conclusion: MRgRT for hepatocellular carcinoma was safe without severe gastrointestinal toxicities and reach excellent local control. Keywords: MRgRT, HCC, SBRT neoadjuvant chemoradiotherapy as predictive biomarker for nivolumab benefit in esophageal cancer Pim J.J. Damen 1,2 , Gulsah Ozden 3 , Maaike Berbée 4 , Jacco J. de Haan 5 , Sarah Derks 6 , Nadia Haj Mohammad 7 , Erik W. Korevaar 8 , Hanneke W.M. van Laarhoven 6 , Marlinde de Leede 9 , Radhe Mohan 10 , Bianca Mostert 11 , Stella Mook 12 , Remi Nout 1 , Barbara Stam 13 , Famke L. Schneiders 2 , Mathijs L. Tomassen 2 , Joost J.C. Verhoeff 2 , Rob H.A. Verhoeven 6,14 , Fabienne A.R.M. Warmerdam 15 , Christina T. Muijs 8 , Steven H. Lin 3 , Peter S.N. van Rossum 2 Mini-Oral 4899 Radiation-induced lymphopenia during 1 Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands. 2 Department of Radiation Oncology, Amsterdam UMC location VUmc, Amsterdam, Netherlands. 3 Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA. 4 Department of Radiation Oncology (Maastro), GROW School for Oncology and Reproduction, Maastricht University Medical Centre, Maastricht, Netherlands. 5 Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands. 6 Department of Medical Oncology, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands. 7 Department of Medical Oncology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands. 8 Department of Radiotherapy, University Medical Center Groningen, Groningen, Netherlands. 9 Central Diagnostic Laboratory, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands. 10 Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA. 11 Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, Netherlands. 12 Department of Radiotherapy, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.
Digital Poster 4843
Treatment Outcomes of Stereotactic Body Radiation Therapy (SBRT) using magnetic resonance guided radiotherapy (MRgRT) for Hepatocellular Carcinoma. Makoto Saito 1 , Asuka Kodate 1 , Aki Kanazawa 1 , Rintaro Harada 1 , Miho Watanabe 2 , Takashi Uno 2 1 Radiology, Chiba University Hospital, Chiba, Japan. 2 Diagnostic Radiology and Radiation Oncology, Chiba University, Chiba, Japan Purpose/Objective: We report treatment outcome of SBRT for hepatocellular carcinoma using marker less position registration with MRgRT. Material/Methods: Between December 2021 to January 2025, 25 patients for 29 liver lesions underwent stereotactic body radiation therapy (SBRT) using marker less position verification with MRgRT. Gross tumor volume (GTV) =clinical target volume (CTV), internal target volume (ITV) was created using four-dimensional computed tomography, ITV + 5 mm = planning target volume (PTV), PTV – planning organ at risk volume (PRV) = PTV opt, and the prescribed dose was 37.5 Gy in 5 fractions to the PTV opt. The median prescribed dose was 40 Gy in 5 fractions (range 35 Gy–40 Gy). Rigid registration was based on the GTV of T2-weighted images acquired via the Navigator echoes in each treatment session. The 1-year overall survival, 1-year local control, acute gastrointestinal toxicities, and late gastrointestinal toxicities were evaluated respectively. Results: The median follow up was 20 months (range 5–41 months). The median history of local treatment for hepatocellular carcinoma was 2 (range 0-7), and initial
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