title: Gamma knife radiosurgery for vestibular schwannomas: tumor control and functional preservation in 70 patients.
abstract: OBJECTIVE
  We present the previously unreported outcomes of 70 patients treated with Gamma knife radiosurgery for vestibular schwannoma (VS), including comprehensive analysis of clinical outcomes and the effects of lower marginal doses.
  
  
  METHODS
  We performed a retrospective study of patients treated for VS at Gamma knife of Spokane between 2003 and 2008. Endpoints measured include tumor control, hearing preservation, and facial nerve preservation, including the effect of tumor size and marginal dose. Statistical analysis was performed with Wilcoxon signed-rank test, paired Student t test, Mann-Whitney U test, Kendall's rank correlation, Fisher exact test, and Liddell's exact χ(2) test for matched pairs.
  
  
  RESULTS
  With a mean follow-up of 26 months, 93.8% of tumors either shrank or remained static after receiving a mean marginal dose of 12.7 Gy. Tumor control was independent of marginal dose or tumor size. Hearing preservation was achieved in 64% of patients with serviceable function before the treatment. Hearing changes were independent of dose or tumor size. Preservation of good facial nerve function was achieved in 95% of patients. Post-treatment hydrocephalus occurred in 4.4% of patients, but no other significant morbidities were elucidated.
  
  
  CONCLUSIONS
  In the treatment of VS, contemporary radiosurgical techniques and the use of marginal doses below 13 Gy offer excellent tumor control, at high rates relative to surgical intervention. These findings are independent of marginal dose and tumor size. Patients should be informed about the benefits and risks of radiosurgery and microsurgery before choosing an intervention. Further analysis of post-treatment outcomes should be encouraged as follow-up times increase and the treatment protocols continue to evolve.
authors.affiliation: Gamma Knife of Spokane, Spokane, WA, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Arthurs
authors.forename: Wayne T
authors.initials: WT
authors.lastname: Lamoreaux
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Mackay
authors.forename: John J
authors.initials: JJ
authors.lastname: Demakas
authors.forename: Neil A
authors.initials: NA
authors.lastname: Giddings
authors.forename: Robert K
authors.initials: RK
authors.lastname: Fairbanks
authors.forename: Barton S
authors.initials: BS
authors.lastname: Cooke
authors.forename: Ameer L
authors.initials: AL
authors.lastname: Elaimy
authors.forename: Ben
authors.initials: B
authors.lastname: Peressini
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001299:Audiometry; D005155:Facial Nerve Diseases / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006261:Headache / Q000209:etiology; D034381:Hearing Loss / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000150:complications / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D016634:Radiosurgery / Q000009:adverse effects; D012189:Retrospective Studies; D013997:Time Factors; D014012:Tinnitus / Q000209:etiology; D016896:Treatment Outcome; D014717:Vertigo / Q000209:etiology