Stereotactic Radiosurgery as the First Line Treatment for Intracanalicular Vestibular Schwannomas

• Published in: Neurosurgery Vol. 67; no. Supplement_1
• Main Authors: Ogino, Akiyoshi, Kano, Hideyuki, Long, Hao, Johnson, Stephen, Faramand, Andrew M, Niranjan, Ajay, Flickinger, John, Lunsford, L. Dade
• Format: Journal Article
• Language: English
• Published: Philadelphia Wolters Kluwer Health, Inc 01-12-2020
• Subjects: Ears & hearing; Neurosurgery; Otolaryngology; Radiation therapy; Radiosurgery; Surgical techniques; Tumors
• ISSN: 0148-396X; 1524-4040
• DOI: 10.1093/neuros/nyaa447_883

INTRODUCTION Stereotactic radiosurgery (SRS) using Leksell Gamma knife has become a popular therapeutic option for vestibular schwannomas (VS) because it effectively prevents tumor growth while enhancing hearing and facial nerve function preservation. METHODS Between 1987 and 2017, we identified 209 patients who underwent SRS as the primary intervention for intracanalicular VS. The median age was 54 years, 94 patients were male and 115 were female. Three patients had facial neuropathy at the time of SRS. 155 patients (74%) had serviceable hearing at the time of SRS. The median tumor volume was 0.17 cm3. The tumors were categorized by anatomic location in the internal auditory canal (IAC): lateral-canal, midcanal, medial-canal, and holocanal. Patients with midcanal and medial-canal tumors had significantly better hearing pure tone averages (PTA) compared to patients whose tumors filled the entire IAC (holocanal patients) (P = .034 and P = .047). The median margin dose was 12.5 Gy. The median maximum dose was 24.0 Gy. RESULTS The progression free survival of all intracanalicular VS patients was 97.5% at 3 years, 95.6% at 5 years, and 92.1% at 10 years. The serviceable hearing preservation rate in Gardner-Robertson (GR) grade I & II patients at the time of SRS was 76.6% at 3 years, 63.5% at 5 years, and 27.3% at 10 years. In univariate analysis, younger age (<55 years), GR grade I and smaller tumor volumes (<0.14 cm3) were significantly associated with improved hearing preservation. In multivariate analysis, GR grade I at the time of SRS was significantly associated with improved hearing preservation (p <0.001, HR 3.155, 95% CI 1.71-5.82). The hearing preservation rate of patients with GR grade I VS was 88.1% at 3 years, 77.9% at 5 years, and 38.1% at 10 years. In the analysis by primary anatomic location in the IAC, holocanal tumors were associated with worse hearing preservation (P = .029). CONCLUSION SRS provided sustained tumor control in >90% of Koos Grade I VS patients at 10 years. Hearing was better preserved if the tumor did not involve the entire IAC.