title: Stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of acoustic schwannomas: comparative observations of 125 patients treated at one institution.
abstract: BACKGROUND
  Stereotactic radiosurgery (SRS) and, more recently, fractionated stereotactic radiotherapy (SRT) have been recognized as noninvasive alternatives to surgery for the treatment of acoustic schwannomas. We review our experience of acoustic tumor treatments at one institution using a gamma knife for SRS and the first commercial world installation of a dedicated linac for SRT.
  
  
  METHODS
  Patients were treated with SRS on the gamma knife or SRT on the linac from October 1994 through August 2000. Gamma knife technique involved a fixed-frame multiple shot/high conformality single treatment, whereas linac technique involved daily conventional fraction treatments involving a relocatable frame, fewer isocenters, and high conformality established by noncoplanar arc beam shaping and differential beam weighting.
  
  
  RESULTS
  Sixty-nine patients were treated on the gamma knife, and 56 patients were treated on the linac, with 1 NF-2 patient common to both units. Three patients were lost to follow-up, and in the remaining 122 patients, mean follow-up was 119 +/- 67 weeks for SRS patients and 115 +/- 96 weeks for SRT patients. Tumor control rates were high (> or =97%) for sporadic tumors in both groups but lower for NF-2 tumors in the SRT group. Cranial nerve morbidities were comparably low in both groups, with the exception of functional hearing preservation, which was 2.5-fold higher in patients who received conventional fraction SRT.
  
  
  CONCLUSIONS
  SRS and SRT represent comparable noninvasive treatments for acoustic schwannomas in both sporadic and NF-2 patient groups. At 1-year follow-up, a significantly higher rate of serviceable hearing preservation was achieved in SRT sporadic tumor patients and may therefore be preferable to alternatives including surgery, SRS, or possibly observation in patients with serviceable hearing.
authors.affiliation: Department of Neurosurgery, Thomas Jefferson University Hospital-Wills Neurosensory Institute, Philadelphia, PA 19107, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Andrews
authors.forename: O
authors.initials: O
authors.lastname: Suarez
authors.forename: H W
authors.initials: HW
authors.lastname: Goldman
authors.forename: M B
authors.initials: MB
authors.lastname: Downes
authors.forename: G
authors.initials: G
authors.lastname: Bednarz
authors.forename: B W
authors.initials: BW
authors.lastname: Corn
authors.forename: M
authors.initials: M
authors.lastname: Werner-Wasik
authors.forename: J
authors.initials: J
authors.lastname: Rosenstock
authors.forename: W J
authors.initials: WJ
authors.lastname: Curran
mesh_terms: D000328:Adult; D003056:Cochlear Nerve / Q000528:radiation effects; D019583:Dose Fractionation, Radiation; D005154:Facial Nerve / Q000528:radiation effects; D005260:Female; D005500:Follow-Up Studies; D005684:Gait / Q000528:radiation effects; D006319:Hearing Loss, Sensorineural / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016518:Neurofibromatosis 2 / Q000150:complications / Q000473:pathology / Q000601:surgery; D009464:Neuroma, Acoustic / Q000150:complications / Q000473:pathology / Q000601:surgery*; D010315:Particle Accelerators; D015143:Philadelphia / Q000453:epidemiology; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014717:Vertigo / Q000453:epidemiology / Q000209:etiology