title: Pretreatment growth rate predicts radiation response in vestibular schwannomas.
abstract: OBJECTIVE
  Vestibular schwannomas (VS) are often followed without initial therapeutic intervention because many tumors do not grow and radiation therapy is associated with potential adverse effects. In an effort to determine whether maximizing initial surveillance predicts for later treatment response, the predictive value of preirradiation growth rate of VS on response to radiation therapy was assessed.
  
  
  METHODS
  Sixty-four patients with 65 VS were treated with single-fraction stereotactic radiation surgery or fractionated stereotactic radiation therapy. Pre- and postirradiation linear expansion rates were estimated using volumetric measurements on sequential magnetic resonance images (MRIs). In addition, postirradiation tumor volume change was classified as demonstrating shrinkage (ratio of volume on last follow-up MRI to MRI immediately preceding irradiation <80%), stability (ratio 80%-120%), or expansion (ratio >120%). The median pre- and postirradiation follow-up was 20.0 and 27.5 months, respectively. Seven tumors from neurofibromatosis type 2 (NF2) patients were excluded from statistical analyses.
  
  
  RESULTS
  In the 58 non-NF2 patients, there was a trend of correlation between pre- and postirradiation volume change rates (slope on linear regression, 0.29; P=.06). Tumors demonstrating postirradiation expansion had a median preirradiation growth rate of 89%/year, and those without postirradiation expansion had a median preirradiation growth rate of 41%/year (P=.02). As the preirradiation growth rate increased, the probability of postirradiation expansion also increased. Overall, 24.1% of tumors were stable, 53.4% experienced shrinkage, and 22.5% experienced expansion. Predictors of no postirradiation tumor expansion included no prior surgery (P=.01) and slower tumor growth rate (P=.02). The control of tumors in NF2 patients was only 43%.
  
  
  CONCLUSIONS
  Radiation therapy is an effective treatment for VS, but tumors that grow quickly preirradiation may be more likely to increase in size. Clinicians should take into account tumor growth rate when counseling patients about treatment options.
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts; Harvard Medical School, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Nina N
authors.initials: NN
authors.lastname: Niu
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Niemierko
authors.affiliation: Harvard Medical School, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Mykol
authors.initials: M
authors.lastname: Larvie
authors.affiliation: Harvard Medical School, Department of Radiology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts.
authors.forename: Hugh
authors.initials: H
authors.lastname: Curtin
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Jay S
authors.initials: JS
authors.lastname: Loeffler
authors.affiliation: Harvard Medical School, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McKenna
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: hshih@partners.org.
authors.forename: Helen A
authors.initials: HA
authors.lastname: Shih
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006128:Growth; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016518:Neurofibromatosis 2 / Q000473:pathology* / Q000601:surgery*; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D017785:Photons / Q000627:therapeutic use; D011379:Prognosis; D061766:Proton Therapy; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D047368:Tumor Burden