title: Single fraction versus fractionated linac-based stereotactic radiotherapy for vestibular schwannoma: a single-institution experience.
abstract: OBJECTIVE
  To evaluate and compare outcomes for patients with vestibular schwannoma (VS) treated in a single institution with linac-based stereotactic radiosurgery (SRS) or by fractionated stereotactic radiotherapy (SRT).
  
  
  METHODS
  One hundred and nineteen patients (SRS = 78, SRT = 41) were treated. For both SRS and SRT, beam shaping is performed by a mini-multileaf collimator. For SRS, a median single dose of 12.5 Gy (range, 11-14 Gy), prescribed to the 80% isodose line encompassing the target, was applied. Of the 42 SRT treatments, 32 treatments consisted of 10 fractions of 3-4 Gy, and 10 patients received 25 sessions of 2 Gy, prescribed to the 100% with the 95% isodose line encompassing the planning target volume. Mean largest tumor diameter was 16.6 mm in the SRS and 24.6 mm in the SRT group. Local tumor control, cranial nerve toxicity, and preservation of useful hearing were recorded. Any new treatment-induced cranial nerve neuropathy was scored as a complication.
  
  
  RESULTS
  Median follow-up was 62 months (range, 6-136 months), 5 patients progressed, resulting in an overall 5-year local tumor control of 95%. The overall 5-year facial nerve preservation probability was 88% and facial nerve neuropathy was statistically significantly higher after SRS, after prior surgery, for larger tumors, and in Koos Grade ≥3. The overall 5-year trigeminal nerve preservation probability was 96%, not significantly influenced by any of the risk factors. The overall 4-year probability of preservation of useful hearing (Gardner-Robertson score 1 or 2) was 68%, not significantly different between SRS or SRT (59% vs. 82%, p = 0.089, log rank).
  
  
  CONCLUSIONS
  Linac-based RT results in good local control and acceptable clinical outcome in small to medium-sized vestibular schwannomas (VSs). Radiosurgery for large VSs (Koos Grade ≥3) remains a challenge because of increased facial nerve neuropathy.
authors.affiliation: Department of Radiation Oncology, UZ Brussel, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. ccollen@uzbrussel.be
authors.forename: Christine
authors.initials: C
authors.lastname: Collen
authors.forename: Ben
authors.initials: B
authors.lastname: Ampe
authors.forename: Thierry
authors.initials: T
authors.lastname: Gevaert
authors.forename: Maarten
authors.initials: M
authors.lastname: Moens
authors.forename: Nadine
authors.initials: N
authors.lastname: Linthout
authors.forename: Mark
authors.initials: M
authors.lastname: De Ridder
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
authors.forename: Jean
authors.initials: J
authors.lastname: D'Haens
authors.forename: Guy
authors.initials: G
authors.lastname: Storme
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D019583:Dose Fractionation, Radiation; D005154:Facial Nerve / Q000528:radiation effects; D005155:Facial Nerve Diseases / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006309:Hearing / Q000528:radiation effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D059351:Organ Sparing Treatments / Q000379:methods; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D016896:Treatment Outcome; D047368:Tumor Burden; D055815:Young Adult