Upright Image-Guided Proton Therapy for Pediatric Cns, Peri-Cranial, and Ocular Tumors: Early Clinical Outcomes and Medical Physics Experience
Abstract
Purpose
Pediatric central nervous system (CNS), peri-cranial, and ocular tumors pose significant challenges for radiation delivery due to complex target geometries, proximity to critical organs at risk, and heightened sensitivity to radiation-induced toxicity. Proton therapy provides superior dose conformity; however, conventional gantry-based systems impose substantial infrastructure and cost requirements. Upright image-guided proton therapy (IGPT) enables gantry-less delivery and represents a potential paradigm shift toward more compact and accessible proton therapy systems. This study reports early clinical outcomes and medical physics experience with upright IGPT in pediatric patients, with a focus on immobilization, image guidance, positioning reproducibility, and treatment workflow feasibility.
Methods
A prospective cohort of ten pediatric and adolescent patients treated with upright IGPT between January 2024 and December 2025 was analyzed. Indications included CNS, peri-cranial, and ocular malignancies, including craniospinal irradiation (CSI) and re-irradiation cases. Dedicated upright immobilization systems were used, with daily image guidance employing 2D/3D or 3D/3D registration. Positioning corrections, setup reproducibility, and treatment delivery continuity were assessed. Treatments were delivered with and without monitored anesthesia care, depending on patient age and compliance.
Results
All patients completed upright IGPT without workflow interruptions or positioning-related delays. Upright immobilization was well tolerated, including in children as young as two years. Mean translational setup corrections were within ±2 mm, with rotational corrections within ±2°, demonstrating reproducible positioning across fractions. No treatment sessions required replanning or abandonment due to positioning instability. At three months post-treatment, local control was observed in all patients. No grade ≥3 acute toxicities occurred, and most grade 1–2 toxicities resolved by early follow-up.
Conclusion
This early experience demonstrates that upright IGPT is technically feasible and clinically tolerable for complex pediatric indications, including CSI and re-irradiation. Robust immobilization and daily image guidance enable reproducible positioning suitable for high-precision proton delivery without the need for a rotating gantry.