2515 - Vertebral-Body-Sparing Proton Craniospinal Irradiation in Pediatric Patients: Spinal Growth and Acute Toxicity Outcomes

Purpose/Objective(s): Conventional proton craniospinal irradiation (CSI) typically covers the entire vertebral body in children with skeletal immaturity to prevent asymmetric spinal growth. This study aims to evaluate spinal growth outcomes and acute toxicities in pediatric patients receiving vertebral-body-sparing proton craniospinal irradiation (VBSpCSI) utilizing pencil beam scanning.

Materials/Methods: Seventy pediatric patients treated with VBSpCSI between January 2020 and December 2022 were retrospectively assessed. Spinal development results were evaluated using magnetic resonance imaging by Cobb angle measurement. Acute toxicities were systematically documented through medical record review.

Results: The median age of patients at the time of radiation therapy was 6 years (range 2–16 years). At a median follow-up of 20 months (range 7-45mo), no patient developed scoliosis or reported chronic back pain. During the radiotherapy, almost all patients (n=69, 98.6%) experienced hematologic toxicity. The nadir of white blood cells (WBC) was significantly associated with vertebral body V20 (P < 0.01), age at radiotherapy in months (P < 0.01), and receipt of chemotherapy (P < 0.01). Similarly, the neutrophil nadir was also significantly associated with these factors (all P < 0.05). The incidence of gastrointestinal toxicity and esophagitis was relatively low.

Conclusion: Sparing vertebral bodies in proton CSI significantly reduces acute hematologic toxicities, which is especially important for young children or those requiring chemotherapy. No cases of scoliosis were observed during the follow-up of this study.