Introduction
Optic pathway gliomas (OPGs) are low-grade tumors affecting the visual pathways, accounting for 3-5% of pediatric brain tumors. Overall survival is high, but 70-90% experience visual impairment1,2. Tumors may occur anywhere along the optic pathway, and those affecting the chiasm and post-chiasmatic structures are associated with increased risk of vision impairment. Radiographic response to treatment is poorly correlated with visual outcome, leading visual acuity (VA) to be included as an outcome in modern clinical trials3. Patients with OPG are also vulnerable to visual field (VF) deficits, and there is emerging evidence that VF deficits can be present even in the absence of VA impairment4.
Biologic therapies have emerged as viable alternatives to traditional chemotherapy for the treatment of OPG. Bevacizumab is a monoclonal antibody against the vascular endothelial growth factor (VEGF) with demonstrated anti-tumor efficacy for progressive low-grade glioma, including OPG5. In contrast to traditional chemotherapy, bevacizumab has a direct effect on tumor microenvironment by inhibiting angiogenesis, thereby conferring a theoretical advantage for controlling tumor-related functional impairment. Initial reports of VA outcomes following bevacizumab-based therapy (BBT) are promising. One early case series described favorable vision outcomes in 4 patients with OPG treated with BBT6. Another case series included 6 patients with OPG, 4 of whom had vision improvement after BBT treatment7. In 2022, Green et al published a multicenter cohort study demonstrating VA stabilization or improvement in 50 of 65 children with evaluable outcomes treated with BBT for OPG8. Compared to VA outcomes, VF outcomes are less well-understood, in part because of the relative difficulty of reliable VF assessment and young age of the OPG population. One report of 2 sporadic OPGs with VF deficits, but stable tumor size, had improvement in VF following treatment with BBT9. The Green et al cohort study also assessed VF as a secondary outcome. Although less than a third of the overall cohort had evaluable VF data, 23 of 24 patients included had stable or improved VF after BBT8.
Prospective studies evaluating visual outcomes including VA and VF for patients treated with BBT are ongoing10. In the interim, there is a knowledge gap between the known visual outcomes from traditional chemotherapy regimen and the modern prospective trials of biologic agents. Further characterization of both VA and VF outcomes for patients treated with BBT is needed to inform treatment decisions for patients with vision-threatening OPG. In the present study, we retrospectively assessed visual outcomes for patients treated for OPG with BBT.