ESTRO 2025 - Abstract Book

S1144

Clinical – Head & neck

ESTRO 2025

4543

Digital Poster Proton beam therapy of skull base tumors: A prospective assessment of efficacy and toxicity Louis Feindt 1,2 , Annekatrin Seidlitz 1,2,3 , Elisa Thomas 1,2 , Steffen Appold 1,2,3 , Michael Baumann 4,2,5 , Steffen Löck 1,2,6 , Lydia Koi 1,7,2 , Mechthild Krause 1,8,3 1 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany. 2 OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. 3 National Center for Tumor Diseases Dresden (NCT/UCC), Germany: German Cancer Research Center (DKFZ), Heidelberg, Germany, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany; Helmholtz Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany. 4 German Cancer Research Center (DKFZ), and German Cancer Consortium (DKTK), Core Center Heidelberg, Heidelberg, Germany. 5 German Cancer Research Center (DKFZ) Heidelberg, Division of Radiooncology Radiobiology, Heidelberg, Germany. 6 German Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research Center (DKFZ), Dresden, Germany. 7 Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Oncoray, Dresden, Germany. 8 OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany Purpose/Objective: Proton beam therapy is a promising modality for the treatment of skull base tumors, as it allows for a more precise energy delivery and is more sparing to the surrounding normal tissue than conventional radiotherapy. Previous studies have documented the effectiveness of this modality in terms of local tumor control and survival rates. However, there is limited long-term data on the late toxicities of this treatment. This study aims to evaluate the long-term toxicity of proton beam therapy and to analyze their impact on patients’ quality of life in order to follow a more comprehensive assessment of treatment safety and efficacy. Material/Methods: In this non-randomized, monocentric phase II study, patients with tumors of the skull base received proton beam therapy with curative intent. The total dose and fractionation regimens used, were based on photon therapy standards and published case series on proton beam therapy. Inclusion criteria comprises of patients over 18 years of age with chordomas, chondrosarcomas or salivary gland carcinomas (e.g. adenoid cycstic carinomas), an ECOG ≤ 2 and an indication for high-dose radiotherapy. Patients were excluded, if MRI planning was not possible, if there was a lack of compliance or limitations in reproducible positioning or if metallic structures in the region of interest influenced the dose distribution. The primary outcome of the study was the assessment of grade III/IV toxicity according to CTCAE 4.0. Secondary outcomes included the local tumor control rate at 2 years, overall survival at 2 years, acute toxicities > grade II and late toxicities. Results: Between 2014 and 2021 152 patients were recruited and evaluated. Median follow-up for those patients was 16.7 months. Only 1.5% of all measured values were higher than 2 (CTCAE 4.0). Initial statistical analyses show that the frequency of values > 2 is not significantly above the tolerance limit of 10 % (p-value =1.0). Conclusion: The results of this study to date indicate that proton beam therapy is a promising treatment option for skull base tumors with an acceptable toxicity profile. The study continues to enroll patients and further evaluations will follow to fully assess long-term toxicities and outcomes.

Keywords: particle therapy,proton beam therapy,late toxicity

References: