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.