Real-time and online adaptive particle therapy in 10 years: a Delphi consensus analysis

Real-time and online adaptive particle therapy in 10 years: a Delphi consensus analysis

P. Trnkova1, Y. Zhang2, T. Toshito3, B. Heijmen4, C. Richter5, M. Aznar6, F. Albertini2, A. Bolsi2, J. Daartz7, A. Knopf2,8, J. Bertholet9

1Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
2Center for Proton Therapy, Paul Scherrer Institute; Villigen, Switzerland
3Nagoya Proton Therapy Center, Nagoya City University West Medical Center, Nagoya, Japan
4Department of Radiotherapy, Erasmus University Medical Center (Erasmus MC), Rotterdam, the Netherlands
5 OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden – Rossendorf, Dresden, Germany
6 Division of Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
7Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston MA 02114, United States of America
8 Institute for Medical Engineering and Medical Informatics, School of Life Sciences, University for Applied Sciences and Arts Northwestern Switzerland.
9 Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, Bern, Switzerland

Purpose/objectives: To collect experts’ opinion on the future of Online Adaptive Particle Therapy (OAPT) and Real Time Motion Management (RRMM) for a vision with a ten-year horizon.
Material/Methods: Following the POP-ART PT survey on current status [1], the present 3-round Delphi consensus study addresses the future of OAPT and RRMM with a panel of 11 experts using questionnaires. Second and third rounds were adapted based on the answers from the previous round to generate controlled opinion feedback (Figure 1). Full consensus (FC) or partial consensus (PC) were reached when all experts agreed or only one expert had a different opinion, respectively.
Results: OAPT will be the method of choice in ten years (PC), mainly in case of variable organ filling and performed with a single in-room imaging modality (FC). There was no consensus on whether offline adaptation will still be performed once OAPT is used clinically. All steps of OAPT require automation to maintain patient throughput (FC). Artificial Intelligence is needed for safe automation, with its central role seen in auto-segmentation (FC). Standardising reporting of endpoints in clinical trials (PC) and cumulative dose reporting (PC) is necessary. It is not currently clear what the best and fastest patient QA method for OAPT will be, and further investigations are required to answer this question (FC). As efficient workflows and tools are medical products, the clinical implementation requires cooperation between industry, research and clinic (FC) with automated and fast systems, reliable deformable registration for dose accumulation, and higher quality in-room imaging identified as the top three priorities (PC). The future importance of MRI-guided PT did not reach consensus.
RRMM is needed for near-real-time OAPT and to treat moving targets (FC) as it mitigates dose deteriorations for both, target and OARs (FC). It should combine multiple approaches, including breath-hold, rescanning, gating, or tracking (FC) based on individual patient selection criteria (FC) and pre-treatment motion characteristics (FC). Optimisation of rescanning parameters, motion model uncertainties and pre-treatment 4D evaluation were considered clinically important (FC). The need to report fractional 4D dose distribution in clinical trials did not reach consensus. 4D dose calculation and its uncertainty evaluation were identified as top requirements (FC). 4D log-file dose reconstruction, (surface) image-based gating/tracking, efficient image guidance and on-board MR guidance were considered of interest but without reaching consensus.
Conclusion: A DELPHI consensus analysis was performed to explore needed developments for OAPT and RRMM. Join efforts between industry research and clinics are needed to translate innovations into efficient and clinically feasible workflows for broad-scale implementation. Consistent reporting of well-defined endpoints should be included in clinical trials to evaluate the clinical impact of both methods.
[1] Zhang Y, Trnkova P et al, ESTRO 2021
Key words: Real time motion management, online adaptive particle therapy, consensus opinion