PURPOSE: To investigate the current practice patterns in image-guided proton therapy (IGPT) for extremities.

METHODS: A multi-institutional survey was distributed to European particle therapy centres to analyse the current practice of IGPT for tumours of the extremities. A Delphi consensus analysis was developed to define minimum requirements and optimal workflow for clinical practice within eight centres participating in the European Particle Therapy Network (EPTN).

RESULTS: Eight centres participated in the survey. Patient immobilization methods varied, with supine position being optimal for selected tumor locations in most of the centres and prone position being optional in some centres. Multimodal imaging, in particular magnetic resonance imaging (MRI), was routinely used for across all centres, especially for delineation. Setup verification involved 2D imaging predominantly, with a few centres employing 3D imaging. Imaging for treatment evaluation varied, with differing intervals between treatment and first control computer tomography (CT) scans. Current limitations highlighted the need for improved software tools, streamlined workflow processes, and more comprehensive guidelines. Five centres participated in the Delphi consensus analysis. The full consensus was reached on the use of specific imaging modalities, adaptive techniques, and dedicated protocols for paediatric patients, with a need for standardization and guidelines.

CONCLUSION: There are differences in extremity IGPT clinical practice among European particle therapy centres. The optimal workflow identified by the expert consensus has not yet been reached, partly due to the small number of patients treated annually. To standardize clinical practice and improve IGPT quality for extremity tumours, consensus guidelines are strongly needed.