Early Results With Hypofractionated Gamma Knife Radiotherapy for Treatment of Vestibular Schwannoma

Introduction: Vestibular schwannoma (VS) management with stereotactic radiation previously only included stereotactic radiosurgery with Gamma Knife (GKRS) or LINAC-based radiotherapy (LBR). Hypofractionated Gamma Knife radiotherapy (hfGKRS) is a novel protocol potentially producing less toxicity than the alternatives. This study examines early results in tumor control, complications and hearing preservation outcomes in a consecutive series of vestibular schwannoma patients treated with hfGKRS.

Methods: A retrospective review was conducted for all patients with unilateral VS treated with primary hfGKRS at a single academic center between 2017 and 2023. Pre and post-treatment imaging studies, notes and audiograms were analyzed. Pre and post-treatment tumor volume were tabulated. Audiometric outcomes recorded were pure-tone average (PTA), word recognition score (WRS), and speech reception threshold (SRT). Collected data included pre and post-treatment tinnitus, imbalance, House-Brackmann score, and facial spasms. Outcomes obtained were compared to literature controls of traditional GKRS and LBR.

Results: A total of 33 hfGKRS cases were identified. Mean tumor volume was 1.55 cm3 (range 0.14-8.45 cm3). 28 patients had follow-up imaging and mean patient follow-up was 28 months (range 6-77 months). Pre-treatment PTA for the ipsilateral ear was 63.3dB with WRS of 40% and SRT of 34.7dB. Post-treatment PTA was 74.3dB with WRS of 28.1% and SRT of 44.4dB. Serviceable hearing was preserved in 83% of patients and tumor control was 94%. hfGKRS complications included tinnitus (12.1%), dizziness (9.1%), facial pain (6.1%), and facial spasms (6.1%). Outcomes compared favorably with GKRS and LBR reports.

Conclusions: Multiple factors prior to treatment may influence outcomes. Short term results for VS treated with hfGKRS had high rates of tumor control, favorable hearing results and comparable complication rates to literature reports for both GKRS and LBR. Further follow-up is needed for long-term outcomes in tumor control, toxicity and audiometric results.