Visual decline in pediatric survivors of brain tumors following radiotherapy

Radiotherapy-related visual decline is a significant concern in survivors of childhood cancer; however, data establishing the dose-response relationship between dose to the optic apparatus and visual acuity decline in children are sparse. We aimed to determine this relationship in a cohort of children treated with proton therapy.

We identified 458 children with 875 eyes at risk treated with proton therapy for intracranial malignancy between December 2006 and September 2018. Eyes were considered at risk if either the ipsilateral optic nerve or optic chiasm received ≥30 GyRBE to 0.1 cm³. Kaplan-Meier and Normal Tissue Complication Probability modeling was used to establish the relationship between radiotherapy dose and risk of visual decline.

Excluding children with tumor progression, no patient experienced complete vision loss. The actuarial 5-year rate of any visual acuity decline was 2.6% (95% confidence interval [CI]: 1.5%-4.6%). The dose to 0.1 cm³ of the ipsilateral optic nerve or optic chiasm resulting in a 1%, 5%, and 10% risk of acuity decline were 52.7 GyRBE, 56.6 GyRBE, and 58.3 GyRBE. Visual decline was only seen in children with primary tumors of the optic pathway or suprasellar region.

Visual acuity decline following radiotherapy for intracranial malignancies in children is rare. A dose of approximately 56 GyRBE to 0.1 cm³ results in an approximately 5% risk of visual acuity decline for children with suprasellar or optic pathway tumors. A dose to 0.1 cm³ of 56 GyRBE appears to be safe for children with tumors elsewhere in the brain.