title: Volume changes after stereotactic LINAC radiotherapy in vestibular schwannoma: control rate and growth patterns.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the control rate of vestibular schwannomas (VS) after treatment with linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) or radiotherapy (SRT) by using a validated volumetric measuring tool. Volume-based studies on prognosis after LINAC-based SRS or SRT for VS are reported scarcely. In addition, growth patterns and risk factors predicting treatment failure were analyzed.
  
  
  METHODS
  Retrospectively, 37 VS patients treated with LINAC based SRS or SRT were analyzed. Baseline and follow-up magnetic resonance imaging scans were analyzed with volume measurements on contrast enhanced T1-weighted magnetic resonance imaging. Absence of intervention after radiotherapy was defined as "no additional intervention group, " absence of radiological growth was defined as "radiological control group. " Significant growth was defined as a volume change of 19.7% or more, as calculated in a previous study.
  
  
  RESULTS
  The cumulative 4-year probability of no additional intervention was 96.4% ± 0.03; the 4-year radiological control probability was 85.4% ± 0.1). The median follow-up was 40 months. Overall, shrinkage was seen in 65%, stable VS in 22%, and growth in 13%. In 54% of all patients, transient swelling was observed. No prognostic factors were found regarding VS growth. Previous treatment and SRS were associated with transient swelling significantly.
  
  
  CONCLUSIONS
  Good control rates are reported for LINAC based SRS or SRT in VS, in which the lower rate of radiological growth control is attributed to the use of the more sensitive volume measurements. Transient swelling after radiosurgery is a common phenomenon and should not be mistaken for treatment failure. Previous treatment and SRS were significantly associated with transient swelling.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Maastricht University Medical Centre, the Netherlands. rickvandelangenberg@hotmail.com
authors.forename: Rick
authors.initials: R
authors.lastname: van de Langenberg
authors.forename: Amy J C
authors.initials: AJ
authors.lastname: Dohmen
authors.forename: Bert J
authors.initials: BJ
authors.lastname: de Bondt
authors.forename: Patty J
authors.initials: PJ
authors.lastname: Nelemans
authors.forename: Brigitta G
authors.initials: BG
authors.lastname: Baumert
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Stokroos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007249:Inflammation / Q000175:diagnosis; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*; D011336:Probability; D016634:Radiosurgery / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects*; D057832:Watchful Waiting
chemical_list: D003287:Contrast Media