title: A study on the radiation tolerance of the optic nerves and chiasm after stereotactic radiosurgery.
abstract: OBJECTIVE
  To evaluate the risk of clinically significant radiation optic neuropathy (RON) for patients having stereotactic radiosurgery of benign tumors adjacent to the optic apparatus.
  
  
  METHODS
  We reviewed the dose plans and clinical outcomes of 218 gamma knife procedures (215 patients) for tumors of the sellar and parasellar region (meningiomas, n = 122; pituitary adenomas, n = 89; craniopharyngiomas, n = 7 patients). Previous surgery or radiation therapy was performed in 156 (66%) and 24 (11%) patients, respectively. Median follow-up was 40 months (range 4-115).
  
  
  RESULTS
  The median maximum radiation dose to the optic nerve was 10 Gy (range 0.4-16.0). Four patients (1.9%) developed RON at a median of 48 months after radiosurgery. All had prior surgery, and 3 of 4 had external beam radiotherapy (EBRT) in their management either before (n = 2) or adjuvantly (n = 1). The risk of developing a clinically significant RON was 1.1% for patients receiving 12 Gy or less. Patients receiving prior or concurrent EBRT had a greater risk of developing RON after radiosurgery (p = 0.004).
  
  
  CONCLUSIONS
  RON occurred in less than 2% of our patients, despite the majority (73%) receiving more than 8 Gy to a short segment of the optic apparatus. Knowledge of the dose tolerance of these structures permits physicians to be more aggressive in treating patients with sellar or parasellar tumors, especially those with hormone-producing pituitary adenomas that appear to require higher doses to achieve biochemical remission.
authors.affiliation: Division of Radiation Oncology, Mayo Clinic and Foundation, Rochester, MN 55905, USA. stafford.scott@mayo.edu
authors.forename: Scott L
authors.initials: SL
authors.lastname: Stafford
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Pollock
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Leavitt
authors.forename: Robert L
authors.initials: RL
authors.lastname: Foote
authors.forename: Paul D
authors.initials: PD
authors.lastname: Brown
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Link
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Gorman
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Schomberg
mesh_terms: D000236:Adenoma / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003397:Craniopharyngioma / Q000601:surgery; D016208:Databases, Factual; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000601:surgery; D008579:Meningioma / Q000601:surgery; D008875:Middle Aged; D009897:Optic Chiasm / Q000528:radiation effects*; D009900:Optic Nerve / Q000528:radiation effects*; D009901:Optic Nerve Diseases / Q000453:epidemiology / Q000209:etiology*; D010911:Pituitary Neoplasms / Q000601:surgery; D011446:Prospective Studies; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology*; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000009:adverse effects*; D012306:Risk; D016896:Treatment Outcome