RADT-22. STEREOTACTIC RADIOSURGERY FOR VESTIBULAR SCHWANNOMA WITH RADIOGRAPHIC BRAINSTEM COMPRESSION

Abstract

Abstract BACKGROUND The safety of single treatment stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) with radiographic evidence of brainstem compression- but without motor deficit- is controversial. Data on linac-based SRS in this setting are scarce. We address this deficit in the literature with a report of outcome of an unselected series of patients with VS with radiographic brainstem compression treated with linac SRS our institution. METHODS We included patients with unilateral VS of any size with radiographic brainstem compression at the time of SRS. All patients were without serious brainstem neurologic deficits at the time of SRS. The SRS prescription dose was 12.5 Gy in a single fraction using 6MV photon beams produced by a linear accelerator and delivered with a multiple arc technique. Inclusion in this study required at least 1 year of radiographic follow-up with magnetic resonance imaging (MRI). The primary endpoint was freedom from serious brainstem toxicity (CTCAEv5 grade >3); secondary endpoint was freedom from tumor enlargement considered to represent tumor progression, or any type of enlargement requiring surgical intervention. We also assessed serious cranial nerve complications, excluding hearing loss, defined as CTCAEv5 grade 3 toxicity. RESULTS Among 139 patients, the median MRI follow-up time was 5 years and the median tumor size was 2.5 cm greatest axial dimension and 5cc in volume. The median brainstem D0.03cc = 12.6 Gy, and the median brainstem V10Gy = 0.4cc. At 5 years, the actuarial freedom from serious brainstem toxicity was 100% (zero cases), and freedom from tumor enlargement, either requiring surgery or due to progression, was 90%. The rate of grade 3 facial nerve damage in patients without tumor enlargement was 0.9% (1/113). CONCLUSION Linac-based SRS as delivered in our series for VS with radiographic brainstem compression is safe and effective.