title: Long-term outcomes of Gamma Knife radiosurgery in patients with vestibular schwannomas.
abstract: OBJECTIVE
  The authors sought to determine the long-term tumor control and side effects of Gamma Knife radiosurgery (GKRS) in patients with vestibular schwannomas (VS).
  
  
  METHODS
  One hundred seventeen patients with VS underwent GKRS between January 1997 and February 2003. At the time of analysis, at least 5 years had passed since GKRS in all patients. The mean patient age was 60.9 years. The mean maximal tumor diameter was 1.77 ± 0.71 cm. The mean tumor volume was 1.95 ± 2.42 ml. Eighty-two percent of lesions received 1300 cGy and 14% received 1200 cGy. The median dose homogeneity ratio was 1.97 and the median dose conformality ratio was 1.78. Follow-up included MR imaging or CT scanning approximately every 6-12 months. Rates of progression to surgery were calculated using the Kaplan-Meier method.
  
  
  RESULTS
  Of the 117 patients in whom data were analyzed, 103 had follow-up MR or CT images and 14 patients were lost to follow-up. Fifty-three percent of patients had stable tumors and 37.9% had a radiographically documented response. Imaging-documented tumor progression was present in 8 patients (7.8%), but in 3 of these the lesion eventually stabilized. Only 5 patients required a neurosurgical intervention. The estimated 1-, 3-, and 5-year rates of progression to surgery were 1, 4.6, and 8.9%, respectively. One patient (1%) developed trigeminal neuropathy, 4 patients (5%) developed permanent facial neuropathy, 3 patients (4%) reported vertigo, and 7 patients (18%) had new gait imbalance following GKRS.
  
  
  CONCLUSIONS
  Gamma Knife radiosurgery results in excellent local control rates with minimal toxicity for patients with VS. The authors recommend standardized follow-up to gain a better understanding of the long-term effects of GKRS.
authors.affiliation: Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors.forename: Erin S
authors.initials: ES
authors.lastname: Murphy
authors.forename: Gene H
authors.initials: GH
authors.lastname: Barnett
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vogelbaum
authors.forename: Gennady
authors.initials: G
authors.lastname: Neyman
authors.forename: Glen H J
authors.initials: GH
authors.lastname: Stevens
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Cohen
authors.forename: Paul
authors.initials: P
authors.lastname: Elson
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Vassil
authors.forename: John H
authors.initials: JH
authors.lastname: Suh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D011788:Quality of Life; D016634:Radiosurgery / Q000295:instrumentation*; D016896:Treatment Outcome