Long-term visual acuity outcomes after radiation therapy for sporadic optic pathway glioma.

Purpose: Children with sporadic optic pathway glioma (OPG) commonly experience a decline in visual acuity (VA). This study aimed to quantify long-term VA outcomes after definitive radiation therapy (RT).
Methods: From 1997 to 2017, 41 patients underwent RT for OPG and had baseline VA testing. All patients underwent serial VA testing every 3-6 months during the first 5 years and annually thereafter. The cumulative incidence of VA decline or improvement (per eye) was estimated using death as a competing risk.
Results: Mean follow-up was 5 years. Most tumors (93%) involved the postchiasmatic optic tracts and/or hypothalamus. Of the tumors tested for BRAF alterations (n = 15), 67% had a BRAF fusion. Median time to VA decline was 20 months in the eye with worse vision and 22 months in the better eye. For the worse eye, the 5-year cumulative incidences of VA decline and improvement were 17.9% [95% confidence interval (CI) 7-32.8%] and 13.5% (95% CI 4.7-26.7%), respectively. For the better eye, the 5-year cumulative incidences of VA decline and improvement were 11.5% (95% CI 3.5-30.7%) and 10.6% (95% CI 2.6-25.2%), respectively. Visual outcomes did not correlate with radiographic evidence of tumor progression.
Conclusions: The 5-year cumulative incidence of VA decline was low. VA decline is most likely to occur within the first 2 years after RT and is not associated with radiographic progression of disease, highlighting the need for frequent ophthalmologic exams during this period.