Initial Clinical Experience with Upright Image-Guided Proton Therapy for Pediatric CNS, Pericranial, and Ocular Malignancies

Purpose: To report early clinical experience with upright image-guided proton therapy (IGPT) delivered using a gantry-less system in pediatric patients with central nervous system (CNS), pericranial, and ocular malignancies Materials and methods: This retrospective observational single-institution study with data taken prospectively included ten pediatric patients (≤18 years) treated with upright IGPT between January 2024 and December 2025. Treatments were delivered using a fixed horizontal beamline combined with robotic six-degree-of-freedom positioning and vertical CT-based image guidance. Feasibility, setup reproducibility, acute toxicity (CTCAE v5.0), and early clinical outcomes were evaluated. Target coverage and organ-at-risk (OAR) doses were assessed using dose–volume histogram (DVH) analysis relative to prescription. Positioning accuracy was quantified using archived 3D/3D and 2D/3D image registrations.
Results: All patients completed treatment without interruption. Mean translational setup corrections were within ±5 mm and rotational corrections within ±2° for both pre-irradiation and intra-irradiation verification. Target coverage was consistent with prescription intent, with CTV D95% closely matching prescribed doses (45–70 GyRBE) in single-phase treatments and appropriate dose escalation in boost phases for multi-phase treatments. ... mehrSerial OAR doses
remained constrained relative to prescription across all cases. At three months post-treatment, local control was achieved in all evaluable patients, with complete or partial metabolic response in six patients and stable disease in four.
Conclusions: Upright IGPT using a gantry-less system is feasible in pediatric patients, providing accurate positioning, prescription-compliant dosimetry, and favorable early clinical outcomes in complex CNS, pericranial, and ocular indications.