RADT-17. RADIOTHERAPY IN THE MANAGEMENT OF OPTIC NERVE SHEATH MENINGIOMAS: AN INTERNATIONAL SYSTEMATIC REVIEW AND META-ANALYSIS OF EIGHTEEN STUDIES

Abstract INTRODUCTION Optic nerve sheath meningiomas (ONSMs) are often managed with radiotherapy (RT) with the goal of achieving radiographic local control (LC) to prevent further decline in visual acuity (VA); however, reports on outcomes are limited to small retrospective series. Thus, we aimed to perform a systematic review and meta-analysis of outcomes for patients with ONSM treated with RT. METHODS A PICOS/PRISMA/MOOSE selection criteria was utilized to identify studies for inclusion. Primary outcomes were stable or improved VA and radiographic LC at last follow-up. The secondary outcome was incidence of radiation-induced retinopathy. Weighted random effects meta-analyses using the DerSimonian and Laird methods were conducted to characterize effect sizes. Mixed effects regression models were used to examine potential correlations between gross tumor volume (GTV) and outcomes. RESULTS In total, 381 patients with ONSM across 18 published studies were included. Of these, 332 and 386 treated ONSMs had information on VA or LC, respectively. Median age was 46.75 (range: 9-87), median/mean GTV was 2.905cc (range: 0.28-26.3), and median follow-up was 51.15 months (range: 1-248.4 months). The estimated LC rate at last follow-up was 100% (95% CI: 98-100%), and the estimated proportion of patients with stable or improved VA at last follow-up was 89% (95% CI: 84-93%). The rate of chronic radiation retinopathy was estimated to be 7% (95% CI: 5-11%). GTV was significantly associated with VA (p=0.014) with estimated VA rates of 96.4%, 91.4%, and 80.5% for GTVs of 2.0, 3.0, and 4.0ccs, respectively. CONCLUSIONS RT was well-tolerated in the treatment of ONSM with excellent LC achieved. Nearly 90% of patients noted either stability or improvement in VA. Larger ONSMs were found to be associated with poorer VA. Incidences of radiation-induced retinopathy were limited and estimated to be less than 10%.