ESTRO 2024 - Abstract Book

S95 ESTRO 2024 Particle therapy is especially sensitive to set-up and anatomical variations due to the characteristic depth-dose curve, known as the Bragg peak. It can therefore likely benefit even more from online and real-time adaptation than photon therapy. However, the particles’ characteristics require different accuracy standards and solutions for the processes and algorithms involved. RAPTOR, a consortium supported by the European Union’s Horizon 2020, is dedicated to advancing online and Real-time Adaptive Particle Therapy of canceR (RAPTOR). With 15 PhD projects spanning Europe, RAPTOR focuses on refining treatment adaptation processes covering imaging, intervention, and verification. The work package “Intervention” addresses strategic actions or adjustments during the treatment course in response to expected and/or observed anatomical variations. These interventions are designed to ensure accuracy and effectiveness of particle therapy together with efficient workflows. The work package combines the collaborative efforts of five diverse PhD projects, each approaching the challenges of anatomical variations from different angles. An overview of the students, their projects and supervisors is given in figure 1. The ultimate objective is to provide treatment intervention solutions suitable for different cancer sites, facilities and resource constraints. Online adaptive particle therapy requires fast algorithms that lead to a deliverable plan tailored to the daily anatomy. The studies of the early stage researchers cover essential aspects with the development of a new fast re-optimization algorithm and a tool for daily plan approval. Furthermore, the effectiveness of proposed online plan optimization strategies was evaluated, ranging from spot number and spot placement restricted to comprehensive full re optimization techniques. These approaches are complemented by the development of an upfront plan evaluation method to identify patients who may benefit most from online adaptation and of robust treatment planning methods with different adaptation schemes for anatomical variations as alternative solutions. In the presence of intra-fractional motion, the computational burden increases when adapting 4D robust plans. Therefore, a 4D robust adaptation approach based on dose mimicking was proposed. The ultimate solution for these cases, however, is envisioned to be real-time motion management. The studies on the development and implementation of a fast real-time 4D-dose reconstruction system play a crucial role for the clinical implementation of real-time adaptive particle therapy. The presentation will highlight the outcome of selected studies by our early stage researchers working on these projects of the RAPTOR Intervention work package. Invited Speaker

Figure 1: Overview of the early stage researchers and their projects (top row) as well as their supervisors (bottom row) involved in the RAPTOR work package ”Intervention”