Discussion
Vision impairment represents a major cause of morbidity in children with optic pathway glioma. Biologic therapies including bevacizumab have demonstrated promising results for radiographic tumor burden, but the effect on visual function is less well understood. In the present study, we describe a cohort of children with OPG treated with BBT, a majority of whom had progressive disease, clinically significant baseline visual impairment, and predominantly chiasmatic/post-chiasmatic tumors. The rate of VA stabilization or improvement in the cohort was 82%, consistent prior reports of VA in pediatric low-grade glioma treated with BBT8. By comparison, visual outcomes for carboplatin and vincristine, the traditional first-line chemotherapy regimen for OPG, has more modest effect on vision, with VA stabilization or improvement between 59 and 66%12-14.
The effect of BBT on VF outcomes is not well described, although recent reports have identified VF deficits to be prevalent in OPG even in the absence of VA impairment4. In our cohort, baseline VF deficits were common, occurring in 8 of 9 patients with evaluable fields, and stable or improved VF was observed in 6 (66%) of these patients. Notably, 2 patients experienced deterioration in VF despite stable VA, highlighting the importance of monitoring VF to assess response in OPG-directed therapies.
In conclusion, BBT is associated with favorable visual outcomes for both VA and VF in most patients with OPG in this retrospective cohort. Larger, prospective studies are needed to better understand patient and tumor characteristics that predict favorable response to BBT; however, the results of this cohort, and from other published reports, suggest that bevacizumab is a promising biological therapy for vision preservation.