Long-Term Tumor Control Rates Following Gamma Knife Radiosurgery for Acoustic Neuroma

Acoustic neuromas (ANs) are benign intracranial tumors that arise from myelin-forming Schwann cells surrounding the vestibular branch of the vestibulocochlear nerve (cranial nerve VIII). Treatment options for AN include observation, radiosurgery, and microsurgical resection. Gamma Knife radiosurgery (GKRS) for AN has well-documented short-term safety and efficacy for carefully selected patients. Recent innovations in GKRS technology may improve long-term outcomes. The aim of this study was to report long-term tumor control and complication rates after GKRS for sporadic AN.

A retrospective review was performed of patients with sporadic ANs at Keck Hospital of USC who underwent GKRS from 1995 to 2015 with a minimum follow-up of 12 months.

Median age at treatment was 63.7 years (range, 19.4-84.2 years). Median follow-up time was 69 months. Median tumor diameter was 17.5 mm (range, 5.0-29.0 mm), and median treatment volume was 2.41 cm³ (range, 0.09-12.8 cm³). Median prescribed dose was 12.50 Gy. Tumor control was achieved in 51 (98.1%) patients over the follow-up period (12-192 months). One patient experienced tumor progression at 22 months after GKRS, requiring surgical intervention, which ultimately resulted in remission. Complications included hearing loss (17.3%), worsened balance/ataxia (7.7%), and hydrocephalus (1.92%).

Patients undergoing GKRS for sporadic ANs had high rates of tumor control over a median follow-up time of >5 years. Improvements in radiosurgery treatment planning were seen in the most recent cohort of patients. GKRS is a safe and effective modality for treating sporadic ANs in selected patients.