Evolution of Stereotactic Radiosurgery for Vestibular Schwannomas: A Single-Center Experience Over 30 Years

Background and Objective Over the past 30 years, vestibular schwannomas (VS) have been increasingly treated with stereotactic radiosurgery (SRS). At our institution, SRS was delivered to such tumors first with a Model U gamma knife [GK] (1994–2011), then with a Cyber-knife [CK] (2011–2014), and finally with a Perfexion Model GK (2014 till present). We aim to present our institutional experience analyzing the outcome of such treatment in our cohort.

Methods A retrospective review was conducted for all patients undergoing SRS for VS at our institution from 1994 to 2017. Patient demographics, symptoms, tumor variables, radiosurgery variables, and outcome data were assessed.

Results Our cohort included a total of 111 patients, including 52 treated in the period 1994–2011, 31 treated in the period 2011–2014 (CK), and 28 in the period 2014–2017. Sixty-three percent of the cohort were male, with a predominance of Caucasians (97%) and non-Hispanics (88%). The mean age was 59.7 ± 13.8 with 25% of patients older than 70 years. There was a slight preponderance of left-sided tumors (53%) of which 42% had documented growth prior to treatment. 11% of patients had prior treatment (8% craniotomy; 3% radiation). Prior to SRS, the majority of patients experienced hearing loss (90%), imbalance (53%), and tinnitus (51%). Less commonly reported symptoms included facial weakness (8%), CNV neuropathy (11%), and headaches (19%). The average tumor volume was 1.93 cm³ and 12% of tumors were cystic. The maximum dose to the brainstem was lower in the patients treated with CK than with GK (1.12 vs. 9.23 Gy, p < 0.0001), as was the maximum dose to the cochlea (1.24 vs. 7.54 Gy, p < 0.0001). All patients with normal CNVII function preoperatively retained normal function at last follow-up. Postradiation 7% of patients reported facial twitching. The percent of patients experiencing tinnitus was markedly decreased (34%), although this was not significant (p = 0.09). Fewer patients experienced imbalance postprocedure (27%, p = 0.0081). During the follow-up period, five patients experienced tumor progression.

Conclusion In this cohort, over a 30-year period, radiosurgery using different techniques with different dose delivery/distribution capabilities for vestibular schwannomas resulted in generally excellent rates of tumor control, maintenance of preoperative facial nerve function, and improvement in patient symptoms. There did not appear to be a difference in outcome with respect to technique despite the advances achieved in dose delivery by newer techniques in our cohort.