S2322
Physics - Quality assurance and auditing
ESTRO 2026
evaluation in proton therapy. Material/Methods:
Proffered Paper 111 Robustness Evaluation in Proton Therapy: An ESTRO Delphi Consensus Lamberto Widesott 1 , Erik Korevaar 2 , Gillian Whitfield 3 , Kenneth Jensen 4 , Mischa Hoogeman 5,6 , Emmanuel Jouglar 7 , Eva Van Weerd 6 , Juan M Moreno 8 , Ilaria Rinaldi 9 , Silvia Molinelli 10 , Alessia Pica 11 , Andrew Gosling 12 , Beata Koczur 13 , Christina V Dahlgren 14 , Daniela Alterio 15 , Konrad Urbanek 16 , Lars F Fjæra 17 , Maren Ugland 18 , Maria Tschiche 19 , Marie Vidal 20 , Edmond Sterpin 21,22 , Francesco Fracchiolla 1,23 1 Fisica Sanitaria, APSS, Trento, Italy. 2 Radiation Oncology, University of Groningen, Groningen, Netherlands. 3 Radiotherapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 4 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 5 Radiotherapy, University Medical Center Rotterdam, Rotterdam, Netherlands. 6 Radiotherapy, Holland Proton Therapy Center, Delft, Netherlands. 7 Radiation Oncology, Institut Curie, PSL Research University, Orsay, France. 8 Radiotherapy, Centro de Protonterapia Quironsalud, Madrid, Spain. 9 Radiation Oncology, Maastricht University Medical Centre, Maastricht, Netherlands. 10 10. Medical Physics Unit, CNAO National Center for Oncological Hadrontherapy, Pavia, Italy. 11 Radiotherapy, PSI, Villigen, Switzerland. 12 Radiotherapy Physics, University College London, London, United Kingdom. 13 Radiation Oncology, Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Germany. 14 Medical Physics, The Skandion Clinic, Uppsala, Sweden. 15 Radiotherapy, IEO European Institute of Oncology, Milan, Italy. 16 Radiotherapy, Maria Sk ł odowska-Curie National Research Institute of Oncology, Kraków, Poland. 17 Medical Physics, Oslo University Hospital, Oslo, Norway. 18 Cancer Clinic, Haukeland University Hospital, Bergen, Norway. 19 Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Dresden, Germany.
The consensus was developed within the European Particle Therapy Network (EPTN) Work Package 5. A total of 24 proton therapy centers from 12 European countries participated, with 42 individuals (including 18 radiation oncologists, 23 medical physicists, and one radiation therapist) actively contributing to the study. A writing committee formulated 41 statements (30 Basic and 11 Advanced) based on a systematic review1 and clinical experience. The Delphi consensus process was used, which involved a series of rounds where responses were collected and analyzed blindly. A consensus was reached when at least 75% of responders agreed or disagreed with a statement. Results: Two rounds were needed to finalize the consensus on 28 statements (19 basic, 9 advanced, Table 1 and 2). Key recommendations include: moving away from PTV toward CTV-based robust optimization/evaluation; mandatory inclusion of geometric and range uncertainties; use of worst-case scenario analysis for static targets; and 4DCT-based evaluation for moving targets. It was also agreed that volumetric imaging should be used during treatment for sites prone to anatomical changes to assess plan robustness. In the advanced statements, a high priority was assigned to implementing probabilistic evaluation methods, tools for interplay effect assessment, advanced imaging modalities (such as dual-energy CT and proton CT) to reduce range uncertainty, and integration of variable Relative Biological Effectiveness (RBE) models. Much work concerned reporting of robustness evaluations in clinical workflows, which has provided a solid base for an international guideline on the topic.
20 Radiotherapy, Institut Méditerranéen de Protonthérapie, Nice, France. 21 Oncology,
Experimental Radiotherapy Lab, Leuven, Belgium. 22 Institution de Recherche Exp´erimentale et Clinique, Center of Molecular Imaging Radiotherapy and Oncology (MIRO), Brussels, Belgium. 23 Medical physics, University of Bern, Bern, Switzerland Purpose/Objective: Proton therapy (PT) offers superior dose conformity compared to conventional radiotherapy but is highly sensitive to uncertainties such as patient setup, anatomical changes, and range inaccuracies. Robustness evaluation (RE) is essential to ensure plan quality, yet standardized methodologies are lacking. This ESTRO Delphi consensus aimed to establish clinical guidelines and future priorities for robustness
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