title: Standard-fractionated radiotherapy for optic nerve sheath meningioma: visual outcome is predicted by mean eye dose.
abstract: OBJECTIVE
  Radiotherapy has shown its efficacy in controlling optic nerve sheath meningiomas (ONSM) tumor growth while allowing visual acuity to improve or stabilize. However, radiation-induced toxicity may ultimately jeopardize the functional benefit. The purpose of this study was to identify predictive factors of poor visual outcome in patients receiving radiotherapy for ONSM.
  
  
  METHODS
  We conducted an extensive analysis of 10 patients with ONSM with regard to clinical, radiologic, and dosimetric aspects. All patients were treated with conformal radiotherapy and subsequently underwent biannual neuroophthalmologic and imaging assessments. Pretreatment and posttreatment values of visual acuity and visual field were compared with Wilcoxon's signed rank test.
  
  
  RESULTS
  Visual acuity values significantly improved after radiotherapy. After a median follow-up time of 51 months, 6 patients had improved visual acuity, 4 patients had improved visual field, 1 patient was in stable condition, and 1 patient had deteriorated visual acuity and visual field. Tumor control rate was 100% at magnetic resonance imaging assessment. Visual acuity deterioration after radiotherapy was related to radiation-induced retinopathy in 2 patients and radiation-induced mature cataract in 1 patient. Study of radiotherapy parameters showed that the mean eye dose was significantly higher in those 3 patients who had deteriorated vision.
  
  
  CONCLUSIONS
  Our study confirms that radiotherapy is efficient in treating ONSM. Long-term visual outcome may be compromised by radiation-induced side effects. Mean eye dose has to be considered as a limiting constraint in treatment planning.
authors.affiliation: Neuro-Ophthalmology Unit, Pierre-Wertheimer Hospital, Hospices Civils de Lyon, Lyon, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Abouaf
authors.forename: Nicolas
authors.initials: N
authors.lastname: Girard
authors.forename: Thibaud
authors.initials: T
authors.lastname: Lefort
authors.forename: Anne
authors.initials: A
authors.lastname: D'hombres
authors.forename: Caroline
authors.initials: C
authors.lastname: Tilikete
authors.forename: Alain
authors.initials: A
authors.lastname: Vighetto
authors.forename: Françoise
authors.initials: F
authors.lastname: Mornex
mesh_terms: D000328:Adult; D019583:Dose Fractionation, Radiation; D005123:Eye / Q000528:radiation effects; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*; D008579:Meningioma / Q000175:diagnosis / Q000532:radiotherapy*; D008875:Middle Aged; D019574:Optic Nerve Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal / Q000009:adverse effects* / Q000379:methods; D018709:Statistics, Nonparametric; D014786:Vision Disorders / Q000209:etiology*; D014792:Visual Acuity / Q000502:physiology / Q000528:radiation effects*; D014794:Visual Fields / Q000502:physiology / Q000528:radiation effects