title: Toward dose optimization for fractionated stereotactic radiotherapy for acoustic neuromas: comparison of two dose cohorts.
abstract: OBJECTIVE
  To describe our initial experience of fractionated stereotactic radiotherapy dose reduction comparing two dose cohorts with examination of tumor control rates and serviceable hearing preservation rates.
  
  
  METHODS
  After institutional review board approval, we initiated a retrospective chart review to study the hearing outcomes and tumor control rates. All data were entered into a JMP, version 7.01, statistical spreadsheet for analysis.
  
  
  RESULTS
  A total of 89 patients with serviceable hearing had complete serial audiometric data available for analysis. The higher dose cohort included 43 patients treated to 50.4 Gy with a median follow-up (latest audiogram) of 53 weeks and the lower dose cohort included 46 patients treated to 46.8 Gy with a median follow-up of 65 weeks. The tumor control rate was 100% in both cohorts, and the pure tone average was significantly improved in the low-dose cohort (33 dB vs. 40 dB, p = 0.023, chi-square). When the patient data were analyzed at comparable follow-up points, the actuarial hearing preservation rate was significantly longer for the low-dose cohort than for the high-dose cohort (165 weeks vs. 79 weeks, p = .0318, log-rank). Multivariate analysis revealed the dose cohort (p = 0.0282) and pretreatment Gardner-Robertson class (p = 0.0215) to be highly significant variables affecting the hearing outcome.
  
  
  CONCLUSIONS
  A lower total dose at 46.8 Gy was associated with a 100% local control tumor rate and a greater hearing preservation rate. An additional dose reduction is justified to achieve the optimal dose that will yield the greatest hearing preservation rate without compromising tumor control for these patients.
authors.affiliation: Department of Neurologic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA. david.andrews@jefferson.edu
authors.forename: David W
authors.initials: DW
authors.lastname: Andrews
authors.forename: Maria
authors.initials: M
authors.lastname: Werner-Wasik
authors.forename: Robert B
authors.initials: RB
authors.lastname: Den
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Paek
authors.forename: Beverly
authors.initials: B
authors.lastname: Downes-Phillips
authors.forename: Thomas O
authors.initials: TO
authors.lastname: Willcox
authors.forename: Greg
authors.initials: G
authors.lastname: Bednarz
authors.forename: Mitchell
authors.initials: M
authors.lastname: Maltenfort
authors.forename: James J
authors.initials: JJ
authors.lastname: Evans
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Curran
mesh_terms: D003051:Cochlea / Q000528:radiation effects; D019583:Dose Fractionation, Radiation; D005260:Female; D006309:Hearing / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage / Q000592:standards; D012189:Retrospective Studies