Acoustic Neuroma Treated with Stereotactic Radiosurgery: Follow-up of 335 Patients

OBJECTIVE: To determine the clinical and radiologic outcome of patients with acoustic neuroma (AN) treated with linear accelerator (LINAC) or CyberKnife-based stereotactic radiosurgery with respect to tumor control, preservation of serviceable hearing, and toxicity. METHODS: A retrospective monocentric analysis including all patients who underwent single-fraction LINAC or CyberKnife-based radiosurgery for AN between 1991 and 2015. Patient data were analyzed in terms of radiologic and clinical tumor control (no further intervention needed), treatment-related complications, preservation of serviceable hearing, and objectified hearing loss using pure tone average levels. RESULTS: We included 335 patients (median age 58.2 years, treated either by LINAC-based [n = 270] or CyberKnife [n = 65] stereotactic radiosurgery). The median tumor volume was 1.1 ml (0.1-23.7 ml). The median radiation dose was 12 Gy (LINAC 12 Gy, 11-20 Gy; CyberKnife 13 Gy, 12-13 Gy) at an isodose level of 71.7% (LINAC 68.3%, 31.9%-86.2%; CyberKnife 80%, 65%-81%). The median follow-up was 30 months (LINAC 43 months, 2-224 months; CyberKnife 13 months, 4-37 months). Clinical tumor control was 98%, 89%, and 88% at 2, 5, and 10 years. The objective actuarial hearing preservation rate was 89%, 80%, and 55% at 1, 2, and 5 years. New symptoms were observed in 11.3% and classified as Common Terminology Criteria for Adverse Events grade 1/2, apart from 4 patients (1.2%), who developed Common Terminology Criteria for Adverse Events grade 3. CONCLUSIONS: Our study shows that in AN, high tumor control and considerable hearing preservation rates can be achieved by single-dose radiosurgery at low toxicity rates, resulting in a positive impact on long-term clinical outcome.