Upright positioning in pediatric radiotherapy: rationale, safety considerations and a research roadmap.

Upright positioning is re-emerging as a potential strategy to improve the pediatric radiotherapy experience, particularly for selected children in whom distress, limited cooperation, or repeated general anesthesia represent major barriers to treatment. This practice development report, produced by the Upright Radiotherapy Pediatric Task Group - an international, multiprofessional group bringing together radiation oncology, medical physics, radiation therapy, pediatric anesthesia and industry expertise - reviews the historical rationale, contemporary technological developments, and clinical requirements for evaluating upright pediatric radiotherapy. The considerations discussed apply to both photon and proton delivery, although the current economic and dosimetric drivers are strongest for gantry-less proton systems. The concept is supported by historical experience with seated treatment techniques, recent advances in upright imaging and gantry-less delivery systems, and broader pediatric evidence suggesting that seated positioning may improve procedural tolerability. However, pediatric-specific evidence remains limited, and upright treatment should not be regarded as a universal alternative to conventional supine workflows. Safe translation requires a deliberately cautious framework. Key considerations include age-appropriate immobilization, upright imaging and treatment-planning validation, both day-to-day reproducibility and within-fraction stability of setup, gravity-related anatomical changes, audiovisual distraction, and integration of child-centered preparation strategies. For sedated or anesthetized children, upright positioning introduces specific safety requirements related to airway visibility and access, hemodynamic monitoring, patient support, emergency release, rapid transition to a rescue position, and sufficient free space around the patient for the anesthesia team to intervene. These constraints should be treated as primary design and commissioning requirements rather than secondary workflow adaptations. Near-term research priorities include phantom and anatomical validation studies, assessment of imaging and dosimetric accuracy, emergency workflow testing, and prospective pilot studies evaluating setup reproducibility and within-fraction stability, treatment duration, anesthesia utilization, acute safety, and patient- and caregiver-reported experience. If developed within a rigorous multidisciplinary safety and evidence framework, upright pediatric radiotherapy may become a clinically valuable option for selected children, complementing rather than replacing established supine treatment approaches.