Long-Term Visual Outcomes and Prognostic Indicators following Fractionated Stereotactic Radiotherapy for Optic Nerve Sheath Meningiomas

Purpose/Objective: Fractionated stereotactic radiotherapy (FSRT) is commonly used for the treatment of optic nerve sheath meningiomas (ONSMs) for tumor control and vision preservation. However, long-term visual data in the literature is limited. Our study seeks to determine the efficacy as well as potential prognostic factors for favorable outcomes following FSRT in the treatment of ONSMs.

Methods: Visual and radiographic results were obtained from patients who were treated with FSRT for primary ONSMs between 1997 and 2012. Only patients with complete radiographic and ophthalmologic data prior to and following radiotherapy were included for analysis. Local control was based on radiographic response. Visual outcomes were based on visual acuity, visual fields, and color vision, which were all based on World Health Organization (WHO) and International Statistical Classification (ICD) definitions. Patient vision and treatment characteristics were evaluated for prognostic impact on visual outcomes using chi-squared analysis.

Results: Twenty-nine cases of primary ONSM were identified. Median visual and radiographic follow-up were 7 years (range: 1–22) and 6 years (range: 2–18), respectively. 100% local control was achieved with radiation therapy. 28 of 29 cases obtained radiographic control with a single course of radiotherapy (median dose of 52.2 Gy, range: 50.4–55.8 Gy); one case recurred marginally, and local control was achieved with re-irradiation (dose: 41.4 Gy). Visual outcomes were deemed worsened, stable, or improved in 7 (24%), 11 (38%), and 11 (38%) cases, respectively. Nine of 11 (82%) cases with stable visual outcomes initially presented with minimal to no visual defects. Age 46 years or older, large visual field defects, and color vision defects were significantly associated with worsened visual outcomes following radiotherapy. Presenting visual acuity and time to treatment did not impact visual outcomes.

Conclusion: Our single-institution series provides important long-term radiographic and visual outcomes data for primary ONSMs and contributes to our understanding of this relatively rare tumor. We show that FSRT for ONSMs provides excellent local control and durable stable-to-improved visual outcomes for the majority of patients. Older age (>46 years), large visual field defects, and color vision defects are associated with worsened visual outcomes. The results of this study provide guidance to patients and clinicians when discussing treatment for ONSMs.

No conflict of interest has been declared by the author(s).