title: Long-term outcomes in patients with vestibular schwannomas treated using gamma knife surgery: 10-year follow up.
abstract: OBJECTIVE
  Gamma knife surgery (GKS) has been a safe and effective treatment for vestibular schwannomas in both the short and long term, although less is known about long-term outcomes in the past 10 years. The aim of this study was to clarify long-term outcomes in patients with vestibular schwannomas treated using GKS based on techniques in place in the early 1990s.
  
  
  METHODS
  Eighty patients harboring a vestibular schwannoma (excluding neurofibromatosis Type 2) were treated using GKS between May 1991 and December 1993. Among these, 73 patients were assessed; seven were lost to follow up. The median duration of follow up was 135 months. The mean patient age at the time of GKS was 56 years old. The mean tumor volume was 6.3 cm3, and the mean maximal and marginal radiation doses applied to the tumor were 28.4 and 14.6 Gy, respectively. Follow-up magnetic resonance images were obtained in 71 patients. Forty-eight patients demonstrated partial tumor remission, 14 had tumors that remained stable, and nine demonstrated tumor enlargement or radiation-induced edema requiring resection. Patients with larger tumors did not fare as well as those with smaller lesions. The actuarial 10-year progression-free survival rate was 87% overall, and 93% in patients with tumor volumes less than 10 cm3. No patient experienced malignant transformation.
  
  
  CONCLUSIONS
  Gamma knife surgery remained an effective treatment for vestibular schwannomas for longer than 10 years. Although treatment failures usually occurred within 3 years after GKS, it is necessary to continue follow up in patients to reveal delayed tumor recurrence.
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: Yoshihisa
authors.initials: Y
authors.lastname: Kida
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Mori
authors.forename: Jun
authors.initials: J
authors.lastname: Yoshida
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006311:Hearing Disorders / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D011300:Preoperative Care; D011829:Radiation Dosage; D016634:Radiosurgery / Q000379:methods*; D012720:Severity of Illness Index; D013995:Time; D047368:Tumor Burden