Very Low Dose Stereotactic Radiosurgery for Vestibular Schwannoma

Introduction: While microsurgical resection of vestibular schwannomas yields high rates of disease control, operative morbidity has limited its appeal. In smaller volume lesions, stereotactic radiosurgery has gained favor and has been shown to effectively control tumor growth. Recently, practitioners have employed smaller treatment doses, typically between 12–14 gray, to limit hearing loss and radiation injury to adjacent neurologic structures. Published findings in the literature have been favorable. We have employed even lower doses at our institution, less than 12 gray. We describe here our series, utilizing the lowest doses of stereotactic radiosurgery for vestibular schwannomas thus far reported.

Methods: We examined the records of all patients at our institution that underwent stereotactic radiosurgery between 2004 and 2011, with dosing less than 12 gray to the 50% isodose line. 58 patients were included in the analysis. Serial radiographic and clinical outcomes were monitored.

Results: Median treatment dose was 11.0 gray. Median follow up was 37 months. Overall median progression free survival was 86.0 months. Progression free survival at 1, 2, 3, and 5 years was: 95%, 95%, 73%, and 56% respectively. Hearing preservation rates at 1, 2, 3, and 5 years were 94%, 94%, 88%, and 74% respectively. 0 patients (0.0%) developed post-treatment facial palsy. 3 patients (5.2%) developed dizziness/vertigo. 2 patients (3.4%) developed trigeminal neuralgia. 2 patients (3.4%) required subsequent surgical resection, and 0 patients (0.0%) required repeat radiosurgery.

Conclusions: Treatment with sub 12-gray doses of radiosurgery in vestibular schwannoma appears to produce higher rates of hearing preservation than using higher doses. Cranial neuropathy and vertigo rates are very low. Progression free survival appears to be comparable to published series that utilize higher doses of radiation. Very low dose stereotactic radiosurgery provides effective treatment for vestibular schwannoma with excellent hearing preservation and low side effects.