Ependymoma accounts for 6.7% of all pediatric brain tumors, the majority of which occur in patients under 5 years of age.¹ Though chemotherapeutic regimens have been employed with some benefit,^2–6 the general frontline treatment strategy for localized disease includes maximal safe surgical resection followed by adjuvant focal radiotherapy (RT). Ependymomas can arise anywhere in the brain or spine, but the majority occur in the posterior fossa near the brainstem and other important cranial nerves and structures.⁷ Tumor location and the young age of patients pose technical challenges in achieving local control while minimizing late effects of treatment.

Proton radiotherapy (PRT) is a form of particle radiation that has unique properties which allow for conformal delivery of radiation dose to the target with reduced dose to surrounding normal structures. This reduced radiation exposure to healthy tissues should minimize the incidence and severity of late adverse side effects, which can negatively impact the quality of life of childhood cancer survivors.^8,9 We have previously published early clinical outcomes of 70 pediatric patients with ependymoma who were treated with PRT at our institution.¹⁰ In this study, we report mature clinical outcomes in a large proton treated cohort—including disease control outcomes, patterns of failure, the incidence of neurologic injury and secondary malignancies, and the effects of clinical variables on outcomes.