Single-Fraction vs. Fractionated Stereotactic Radiosurgery for Vestibular Schwannomas with Frameless Radiosurgery: A Single Institution Prospective Observational Study

Abstract

<h3>Purpose/Objective(s)</h3> The number of patients with small- to medium-sized vestibular schwannoma (VS), defined as under 22 mm in greatest dimension, presenting with serviceable hearing has steadily increased over the last 50 years. Thus, treatment of VS often must balance a goal of tumor control with hearing preservation and other potential side effects. Improved hearing rates have been demonstrated with the use of a lower prescription dose. The effect of fractionation in preserving hearing loss is less clear. We sought to evaluate local control and hearing preservation rates in patients treated with single-fraction versus 5-fraction frameless GKRS. <h3>Materials/Methods</h3> Prospectively enrolled patients with a radiographic diagnosis of unilateral vestibular schwannoma who underwent single-fraction or 5-fraction definitive frameless GKRS between 2017 and 2020 were retrospectively reviewed in our institutional review board (IRB) approved database. We used chi-squared tests and t-tests to compare demographic and clinical characteristics by treatment modality. We then used Kaplan-Meier methods to compare the two treatment groups' local control and hearing preservation, and evaluated the statistical significance of the differences by log rank test. <h3>Results</h3> Seventy consecutive patients were treated with single-fraction or fractionated GKRS for VS from 2017 to 2020. Forty-eight patients met inclusion criteria and were included in this analysis. Twenty-three patients underwent single-fraction treatment, and 25 patients underwent fractionated treatment in 5 fractions. Median follow-up time was 2 years for both groups. Patients who were treated with multi-fraction GKRS on average, had a larger maximal tumor diameter than those treated with single-fraction GKRS. At 2 years, radiographic local control of VS treated with single-fraction was 93% compared to 92% for multi-fraction frameless GKRS (p=0.64). No patients required salvage treatment in either group. Hearing preservation was evaluated in patients with available audiograms (13/23 single-fraction and 20/25 multi-fraction). At 2 years, hearing preservation was 46% for patients treated with single-fraction GKRS compared to 78% for patients treated with multi-fraction GKRS, not including patients censored due to lack of available audiogram (p=.06). <h3>Conclusion</h3> Single-fraction and fractionated frameless GKRS provide similar clinical and radiographic local control, while maintaining similar hearing preservation rates, in the treatment of VS.