title: Stereotactic radiosurgery for vestibular schwannomas: analysis of 317 patients followed more than 5 years.
abstract: OBJECTIVE
  Many investigators have reported successful treatment of vestibular schwannomas with gamma knife radiosurgery (GKRS). However, long-term outcomes should be evaluated before concluding that GKRS is truly safe and effective for the treatment of vestibular schwannomas.
  
  
  METHODS
  Between May 1991 and December 1998, 346 consecutive patients (excluding those presenting with neurofibromatosis Type 2) were treated with GKRS. Of these, 317 patients were assessed. Twenty-nine patients were lost to follow-up within 5 years.
  
  
  RESULTS
  The median follow-up period was 7.8 years. Of 301 patients who underwent serial follow-up imaging, two (1%) experienced complete remission, 184 (61%) experienced partial remission, 93 (31%) had stable tumors, and 22 (7%) experienced treatment failure. The actuarial 5- or 10-year progression-free survival (PFS) rate was 93 and 92%, respectively. Tumors less than 15 cm3 in volume (10-yr PFS, 96%; P < 0.001) or which did not compress the brainstem and deviate the fourth ventricle (10-yr PFS, 97%; P = 0.008) resulted in significantly better PFS rates. Failure of treatment usually occurred within 3 years. When the tumor was treated with a marginal dose of 13 Gy or less, the hearing preservation rate was 68%, transient facial palsy developed at a rate of 1%, and facial numbness developed at a rate of 2%.
  
  
  CONCLUSIONS
  GKRS proved to be a safe and effective treatment for patients followed longer than 5 years who presented with tumors with a volume of less than 15 cm3 and who did not have significant fourth ventricle deviation. Good functional outcomes were observed in this group of patients.
authors.affiliation: Department of Neurosurgery, Gamma Knife Center, Komaki City Hospital, Komaki, Japan. h-toshi@komakihp.gr.jp
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Fujitani
authors.forename: Shun
authors.initials: S
authors.lastname: Katsumata
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kida
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: Joji
authors.initials: J
authors.lastname: Koike
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003390:Cranial Nerve Neoplasms / Q000145:classification / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000145:classification / Q000503:physiopathology / Q000601:surgery*; D016016:Proportional Hazards Models; D016634:Radiosurgery / Q000379:methods*; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome