title: Cochlea radiation dose correlates with hearing loss after stereotactic radiosurgery of vestibular schwannoma.
abstract: OBJECTIVE
  For multisession radiosurgery, no published data relate the volume and dose of cochlear irradiation to quantified risk of hearing loss. We conducted a retrospective, dosimetric study to evaluate the relationship between hearing loss after stereotactic radiosurgery (SRS) and the dose-volume of irradiated cochlea.
  
  
  METHODS
  Cochlear dose data were retrospectively collected on consecutive patients who underwent SRS (18 Gy in 3 sessions) for vestibular schwannoma between 1999 and 2005 at Stanford University Hospital. Inclusion criteria included Gardner-Robertson (GR) grade I or II hearing prior to radiosurgical treatment, complete audiograms, and magnetic resonance imaging (MRI) follow-up. A cochlea dose-volume histogram was generated for each of the 94 patients who qualified for this study.
  
  
  RESULTS
  GR grade I-II hearing posttreatment was maintained in 74% of patients (70/94). Median time to last follow-up audiogram was 2.4 years (range 0.4-8.9) and to last MRI was 3.6 years (range 0.5-9.4). Each higher level of cochlear irradiation was associated with increased risk of hearing loss. Larger cochlear volume was associated with lower risk of hearing loss. Controlling for differences in cochlear volume among subjects, each additional mm(3) of cochlea receiving 10 to 16 Gy (single session equivalent doses of 6.6-10.1 Gy3) significantly increased the odds of hearing loss by approximately 5%.
  
  
  CONCLUSIONS
  Larger cochlear volume is associated with lower risk of hearing loss following trisession SRS for vestibular schwannoma. Controlling for this phenomenon, higher radiation dose and larger irradiated cochlear volume are significantly associated with higher risk of hearing loss. This study confirms and quantifies the risk of hearing loss following trisession SRS for vestibular schwannoma.
authors.affiliation: Department of Neurosurgery, Stanford University School of Medicine, Stanford, California, USA.
authors.forename: Melanie G
authors.initials: MG
authors.lastname: Hayden Gephart
authors.forename: Ake
authors.initials: A
authors.lastname: Hansasuta
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Balise
authors.forename: Clara
authors.initials: C
authors.lastname: Choi
authors.forename: Gordon T
authors.initials: GT
authors.lastname: Sakamoto
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Venteicher
authors.forename: Scott G
authors.initials: SG
authors.lastname: Soltys
authors.forename: Iris C
authors.initials: IC
authors.lastname: Gibbs
authors.forename: Griffith R
authors.initials: GR
authors.lastname: Harsh
authors.forename: John R
authors.initials: JR
authors.lastname: Adler
authors.forename: Steven D
authors.initials: SD
authors.lastname: Chang
mesh_terms: D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone; D003051:Cochlea / Q000473:pathology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D034381:Hearing Loss / Q000453:epidemiology* / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D011183:Postoperative Complications / Q000453:epidemiology*; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies; D013063:Speech Discrimination Tests; D055815:Young Adult