Objective: This report evaluates the outcomes of stereotactic radiosurgery (SRS) as the first-line treatment of intracanalicular vestibular schwannomas (VSs).
Methods: Between 1987 and 2017, the authors identified 209 patients who underwent SRS as the primary intervention for a unilateral intracanalicular VS. The median patient age was 54 years (range 22-85 years); 94 patients were male and 115 were female. Three patients had facial neuropathy at the time of SRS. One hundred fifty-five patients (74%) had serviceable hearing (Gardner-Robertson [GR] grades I and II) at the time of SRS. The median tumor volume was 0.17 cm3 (range 0.015-0.63 cm3). The median margin dose was 12.5 Gy (range 11.0-25.0 Gy). The median maximum dose was 24.0 Gy (range 15.7-50.0 Gy).
Results: The progression-free survival rates of all patients with intracanalicular VS were 97.5% at 3 years, 95.6% at 5 years, and 92.1% at 10 years. The rates of freedom from the need for any additional intervention were 99.4% at 3 years, 98.3% at 5 years, and 98.3% at 10 years. The serviceable hearing preservation rates in GR grade I and II patients at the time of SRS were 76.6% at 3 years, 63.5% at 5 years, and 27.3% at 10 years. In univariate analysis, younger age (< 55 years, p = 0.011), better initial hearing (GR grade I, p < 0.001), and smaller tumor volumes (< 0.14 cm3, p = 0.016) were significantly associated with improved hearing preservation. In multivariate analysis, better hearing (GR grade I, p = 0.001, HR 2.869, 95% CI 1.569-5.248) and smaller tumor volumes (< 0.14 cm3, p = 0.033, HR 2.071, 95% CI 1.059-4.047) at the time of SRS were significantly associated with improved hearing preservation. The hearing preservation rates of patients with GR grade I VS were 88.1% at 3 years, 77.9% at 5 years, and 38.1% at 10 years. The hearing preservation rates of patients with VSs smaller than 0.14 cm3 were 85.5% at 3 years, 77.7% at 5 years, and 42.6% at 10 years. Facial neuropathy developed in 1.4% from 6 to 156 months after SRS.
Conclusions: SRS provided sustained tumor control in more than 90% of patients with intracanalicular VS at 10 years and freedom from the need for additional intervention in more than 98% at 10 years. Patients with initially better hearing and smaller VSs had enhanced serviceable hearing preservation during an observation interval up to 10 years after SRS.
Keywords: Gamma Knife surgery; Gardner-Robertson grade; Koos grade; hearing preservation rate; stereotactic radiosurgery; tumor control rate; vestibular schwannoma.