Medium Term Outcome of LINAC-Based Stereotactic Radiosurgery for Vestibular Schwannomas with Marginal Dose of 12.5 Gy

Objective: To determine the outcomes of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) for vestibular schwannomas (VSs) using 12.5 Gy to tumor margin.

Methods: Patients treated between September 2003 and November 2009 were identified from a prospective database. Retrospective review of case notes, radiological imaging, and audiograms were performed.

Results: Fifty patients were treated (23 women, 27 men). The median age was 63 years (range, 21–85 years). The median VS gross tumor volume was 2.35 (range, 0.24–10.59). Presenting symptoms included hearing loss in 43 (86%), balance disorder in 24 (48%), and tinnitus in 19 (38%). Forty-five patients had preoperative pure tone audiogram (PTA); 15 patients had < 50 dB loss at 0.5 kHz, 1 kHz, 2 kHz, and 4 kHz. All patients were treated with a marginal dose of 12.5 Gy using a LINAC equipped with a micro-multileaf collimator. Median follow-up was 4.6 years. There was no tumor growth in the follow-up period, and none of the patients required surgery. Eight audiograms (PTA) were available post-treatment, of which three patients still had <50 dB loss. Nonauditory adverse radiation effects included new or worsened facial nerve palsy (n = 2, 4%; House-Brackmann grades 2 and 5, respectively) and trigeminal sensory disturbance (n = 2, 4%).

Conclusions: LINAC-based SRS with a marginal dose of 12.5 Gy for VS is associated with low complication rates and high rates of tumor control on medium-term follow-up.