Brainstem Toxicity in Pediatric Patients Treated with Protons Using a Single-vault Synchrocyclotron System

Area of Science:

• Pediatric Oncology
• Radiation Oncology
• Neuro-oncology

Background:

• Cranial radiation therapy is crucial for treating pediatric brain tumors.
• Proton beam radiation therapy (PBT) offers reduced collateral dose to normal tissues compared to photon therapy.
• Concerns exist regarding PBT's potential for increased brainstem necrosis risk.

Purpose of the Study:

• To investigate the incidence of brainstem necrosis in pediatric patients treated with PBT for intracranial malignancies.
• To assess the safety profile of passively scattered PBT in a pediatric population.

Main Methods:

• Retrospective review of 58 pediatric patients (≤21 years) treated with PBT between 2013-2018.
• Inclusion criteria: minimum brainstem dose of 50 Gray relative biological effectiveness (GyRBE).
• Brainstem injury assessed using Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

Main Results:

• No patients experienced grade ≥2 brainstem injury.
• One patient had grade 1 toxicity, associated with prior myeloablative chemotherapy and stem cell rescue.
• While some patients exceeded dosimetric constraints, clinical toxicity was minimal.

Conclusions:

• Passively scattered PBT using a single-vault synchrocyclotron demonstrates a low risk of brainstem injury in pediatric patients.
• PBT is a safe and effective treatment option for pediatric intracranial malignancies, with minimal observed brainstem toxicity.