Linear accelerator radiosurgery for nonacoustic schwannomas

Purpose: To analyze the results of nonacoustic schwannomas treated with lin ear accelerator stereotactic radiosurgery. Methods and Materials: Between August 1989 and October 1997, 18 patients wi th nonacoustic schwannomas underwent stereotactic radiosurgery at the Unive rsity of Florida. Nine patients had schwannomas located in the jugular fora men region, seven in the trigeminal nerve, and two in the facial nerve. Nin e patients had initial subtotal resections and nine did not undergo surgica l intervention. One of the 9 patients with subtotal resection was treated w ith radiosurgery for a recurrent tumor. Tumor volumes ranged from 0.7 to 15 .4 cm(3) with a mean volume of 5.5 cm(3). Minimal tumor doses ranged from 1 0.0 to 15.0 Gy with a mean dose of 13.1 Gy. Treatment dose was specified to the 80% isodose shell in 11 patients (58%) and to the 70% isodose shell in the remaining patients. Ten patients (56%) were treated with a single isoc enter, 6 patients (33%) with 2-4 isocenters, and 2 patients (11%) with grea ter than 5 isocenters. Follow-up ranged from 5 to 75 months and the mean fo llow-up was 32 months. Ten patients (56%) had follow-up beyond 2 years and none were lost to follow-up. Local control was defined as clinically stable neurological status and/or stable or decreased tumor size on yearly follow -up MR imaging. Results: Eighteen evaluable patients (100%) had local control after treatme nt. All were alive and progression-free at last follow-up. Six of 10 patien ts with follow-up MRI2 years or more after treatment had tumor regression a nd 4 patients had stable disease. Three additional patients with an MRI at 1 year showed no tumor change. Four complications in 3 patients included on e worsening of a preexisting VII nerve palsy, 2 patients with new onset of hearing loss, and one with ataxia. No surgical intervention or prolonged st eroid use was necessary for any patient with complications. Five patients h ad improvement in preexisting neurologic deficits. Conclusions: Excellent preliminary tumor control rates and a favorable toxi city profile support the effectiveness of linear accelerator stereotactic r adiosurgery for patients with nonacoustic schwannomas. (C) 1999 Elsevier Sc ience Inc.