title: Long-term outcomes and patterns of tumor progression after gamma knife radiosurgery for benign meningiomas.
abstract: OBJECTIVE
  To characterize the timing and patterns of long-term treatment failure after Gamma Knife radiosurgery (GKRS) for benign meningiomas.
  
  
  METHODS
  Data were retrospectively reviewed in 116 patients who underwent 136 GKRS treatments for benign intracranial meningiomas from 1996 to 2004. Patients with atypical or malignant meningiomas were excluded. Surgical resection preceded GKRS in 72 patients (62%). The median tumor volume was 3.4 cm, and the median prescription dose to the 50% isodose line was 16 Gy.
  
  
  RESULTS
  The median follow-up time was 75 months (range, 4-146 months). Overall tumor control was achieved in 128 of 136 lesions (94%), of which tumor size was stable in 68% and decreased in 26%. Seven patients experienced disease progression in 8 tumors, occurring at a mean time of 90 months. The overall 5-year and 10-year actuarial tumor control rate was 98.9% and 84%, respectively. Characteristics corresponding to tumor progression included insufficient tumor coverage (98% vs 93%, P = .007), cavernous sinus lesions, and meningiomatosis. Complications after GKRS developed in 8% of patients, in whom the mean tumor volume was nearly double that in patients with no adverse effects (11 vs 5.7 cm3, P = .003).
  
  
  CONCLUSIONS
  GKRS demonstrates excellent long-term tumor control in the management of benign meningiomas. Tumor progression occurred at a mean time of 7.5 years after GKRS, reinforcing the need for long-term surveillance despite initial tumor control. Treatment failure was related to undercoverage of lesions in the majority of cases, with the remainder demonstrating evidence of abnormal tumor biology.
authors.affiliation: Department of Neurosurgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. gzada@usc.edu
authors.forename: Gabriel
authors.initials: G
authors.lastname: Zada
authors.forename: Paul G
authors.initials: PG
authors.lastname: Pagnini
authors.forename: Cheng
authors.initials: C
authors.lastname: Yu
authors.forename: Kelly T
authors.initials: KT
authors.lastname: Erickson
authors.forename: Jonah
authors.initials: J
authors.lastname: Hirschbein
authors.forename: Vladimir
authors.initials: V
authors.lastname: Zelman
authors.forename: Michael L J
authors.initials: ML
authors.lastname: Apuzzo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D018450:Disease Progression; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008579:Meningioma / Q000473:pathology* / Q000601:surgery*; D008875:Middle Aged; D016634:Radiosurgery / Q000009:adverse effects; D017211:Treatment Failure; D016896:Treatment Outcome; D055815:Young Adult