title: Hypofractionated stereotactic radiation therapy in three to five fractions for vestibular schwannoma.
abstract: OBJECTIVE
  To retrospectively examine the outcomes of hypofractionated stereotactic radiation therapy in three to five fractions for vestibular schwannomas.
  
  
  METHODS
  Twenty-five patients with 26 vestibular schwannomas were treated with hypofractionated stereotactic radiation therapy using a CyberKnife. The vestibular schwannomas of 5 patients were associated with type II neurofibromatosis. The median follow-up time was 80 months (range: 6-167); the median planning target volume was 2.6 cm(3) (0.3-15.4); and the median prescribed dose (≥D90) was 21 Gy in three fractions (18-25 Gy in three to five fractions). Progression was defined as ≥2 mm 3-dimensional post-treatment tumor enlargement excluding transient expansion. Progression or any death was counted as an event in progression-free survival rates, whereas only progression was counted in progression-free rates.
  
  
  RESULTS
  The 7-year progression-free survival and progression-free rates were 78 and 95%, respectively. Late adverse events (≥3 months) with grades based on Common Terminology Criteria for Adverse Events, v4.03 were observed in 6 patients: Grade 3 hydrocephalus in one patient, Grade 2 facial nerve disorders in two and Grade 1-2 tinnitus in three. In total, 12 out of 25 patients maintained pure tone averages ≤50 dB before hypofractionated stereotactic radiation therapy, and 6 of these 12 patients (50%) maintained pure tone averages at this level at the final audiometric follow-up after hypofractionated stereotactic radiation therapy. However, gradient deterioration of pure tone average was observed in 11 of these 12 patients. The mean pure tone averages before hypofractionated stereotactic radiation therapy and at the final follow-up for the aforementioned 12 patients were 29.8 and 57.1 dB, respectively.
  
  
  CONCLUSIONS
  Treating vestibular schwannomas with hypofractionated stereotactic radiation therapy in three to five fractions may prevent tumor progression with tolerable toxicity. However, gradient deterioration of pure tone average was observed.
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Morimoto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Kotsuma
authors.forename: Kana
authors.initials: K
authors.lastname: Adachi
authors.forename: Hiroya
authors.initials: H
authors.lastname: Shiomi
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seo
authors.forename: Masahiko
authors.initials: M
authors.lastname: Koizumi
authors.forename: Naoki
authors.initials: N
authors.lastname: Kagawa
authors.forename: Manabu
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Naoya
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D000328:Adult; D000368:Aged; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D005155:Facial Nerve Diseases / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D016518:Neurofibromatosis 2 / Q000401:mortality / Q000601:surgery*; D009464:Neuroma, Acoustic / Q000401:mortality / Q000601:surgery*; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D016019:Survival Analysis; D014012:Tinnitus / Q000209:etiology
keywords: CyberKnife; acoustic neuroma; stereotactic radiotherapy