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.