Hypofractionated stereotactic radiation therapy for optic nerve sheath meningiomas: A single-center experience and preliminary results.

backgroundPrimary optic nerve sheath meningioma (pONSM) causes progressive vision loss. Surgery carries high morbidity (~ 94% visual impairment), and conventional fractionated radiotherapy (CFRT; 50.4-54 Gy) requires an extended course. Given the low α/β ratio of meningiomas (~ 3.76 Gy), we investigated hypofractionated stereotactic radiotherapy (hypo-FSRT; 40 Gy/10 fx) as an alternative.

methodsThis retrospective STROBE-compliant study (2016-2023) included imaging-confirmed pONSM patients (PS 0-2) unsuitable for or refusing surgery/CFRT. Hypo-FSRT delivered via gamma-ray system with thermoplastic immobilization. PTV = GTV + 3 mm, prescribed to 60% isodose. OAR constraints: optic chiasm/retina/pituitary Dmax ≤ 25 Gy. Visual acuity assessed by Snellen; regression defined as ≥ 1 mm reduction on consecutive MRIs. STATISTICS: paired t-tests, chi-square, logistic regression (OR, 95% CI), Kaplan-Meier with log-rank; p < 0.05 significant. PROGRESSION: any increase in axial/sagittal diameter on ≥ 2 consecutive MRIs. Local control: no progression at last follow-up. Baseline visual impairment duration categorized as acute (≤ 2 months onset-to-RT) or chronic (> 2 months).

results43 patients were included (median follow-up 59 months). Overall vision preservation was 30.2% (13/43). Preservation rates by baseline status: normal 40% (4/10), mild loss 63.6% (7/11), moderate loss 12.5% (1/8), severe loss 7.1% (1/14). Age (OR = 4.21) and mild baseline loss (OR = 7.89) predicted preservation. Tumor control was 100%, regression 76.7% (higher in females: 85.3% vs. 44.4%, p = 0.020). Acute toxicity: reversible ocular pain (16.3%), eyelid edema (13.9%); late retinal hemorrhage (7.0%). No secondary malignancies. Time to blindness was shorter with moderate/severe vs. normal/mild baseline loss (p < 0.001). In post-hoc analysis, acute visual loss (≤ 2 months) showed higher preservation than chronic loss (> 2 months) (62.5% [5/8] vs. 22.9% [8/35]; OR = 5.36). All acute cases were in normal/mild baseline subgroup (preservation: 75.0% and 80.0%, respectively).

conclusionHypo-FSRT yielded 100% tumor control and 76.7% regression, but lower vision preservation (30.2%) than CFRT, particularly with moderate/severe baseline loss. Acute impairment (≤ 2 months) predicts better preservation. Low preservation with normal baseline vision necessitates individualized planning balancing tumor control, vision, and cosmesis. CFRT preferred for vision preservation; optimal fractionation needs prospective validation.