title: Gamma Knife radiosurgery for posterior fossa meningiomas: a multicenter study.
abstract: OBJECTIVE
  Posterior fossa meningiomas represent a common yet challenging clinical entity. They are often associated with neurovascular structures and adjacent to the brainstem. Resection can be undertaken for posterior fossa meningiomas, but residual or recurrent tumor is frequent. Stereotactic radiosurgery (SRS) has been used to treat meningiomas, and this study evaluates the outcome of this approach for those located in the posterior fossa.
  
  
  METHODS
  At 7 medical centers participating in the North American Gamma Knife Consortium, 675 patients undergoing SRS for a posterior fossa meningioma were identified, and clinical and radiological data were obtained for these cases. Females outnumbered males at a ratio of 3.8 to 1, and the median patient age was 57.6 years (range 12-89 years). Prior resection was performed in 43.3% of the patient sample. The mean tumor volume was 6.5 cm(3), and a median margin dose of 13.6 Gy (range 8-40 Gy) was delivered to the tumor.
  
  
  RESULTS
  At a mean follow-up of 60.1 months, tumor control was achieved in 91.2% of cases. Actuarial tumor control was 95%, 92%, and 81% at 3, 5, and 10 years after radiosurgery. Factors predictive of tumor progression included age greater than 65 years (hazard ratio [HR] 2.36, 95% CI 1.30-4.29, p = 0.005), prior history of radiotherapy (HR 5.19, 95% CI 1.69-15.94, p = 0.004), and increasing tumor volume (HR 1.05, 95% CI 1.01-1.08, p = 0.005). Clinical stability or improvement was achieved in 92.3% of patients. Increasing tumor volume (odds ratio [OR] 1.06, 95% CI 1.01-1.10, p = 0.009) and clival, petrous, or cerebellopontine angle location as compared with petroclival, tentorial, and foramen magnum location (OR 1.95, 95% CI 1.05-3.65, p = 0.036) were predictive of neurological decline after radiosurgery. After radiosurgery, ventriculoperitoneal shunt placement, resection, and radiation therapy were performed in 1.6%, 3.6%, and 1.5%, respectively.
  
  
  CONCLUSIONS
  Stereotactic radiosurgery affords a high rate of tumor control and neurological preservation for patients with posterior fossa meningiomas. Those with a smaller tumor volume and no prior radiation therapy were more likely to have a favorable response after radiosurgery. Rarely, additional procedures may be required for hydrocephalus or tumor progression.
authors: 1University of Virginia, Charlottesville, Virginia;
authors: Jason P
authors: JP
authors: Sheehan
authors: 1University of Virginia, Charlottesville, Virginia;
authors: Robert M
authors: RM
authors: Starke
authors: 2University of Pittsburgh, Pennsylvania;
authors: Hideyuki
authors: H
authors: Kano
authors: 5Cleveland Clinic, Cleveland, Ohio;
authors: Gene H
authors: GH
authors: Barnett
authors: 4University of Sherbrooke, Quebec, Canada;
authors: David
authors: D
authors: Mathieu
authors: 6Yale University, New Haven, Connecticut; and.
authors: Veronica
authors: V
authors: Chiang
authors: 6Yale University, New Haven, Connecticut; and.
authors: James B
authors: JB
authors: Yu
authors: 6Yale University, New Haven, Connecticut; and.
authors: Judith
authors: J
authors: Hess
authors: 7Barrow Neurological Institute, Phoenix, Arizona.
authors: Heyoung L
authors: HL
authors: McBride
authors: 7Barrow Neurological Institute, Phoenix, Arizona.
authors: Norissa
authors: N
authors: Honea
authors: 7Barrow Neurological Institute, Phoenix, Arizona.
authors: Peter
authors: P
authors: Nakaji
authors: 3University of Pennsylvania, Philadelphia, Pennsylvania;
authors: John Y K
authors: JY
authors: Lee
authors: 5Cleveland Clinic, Cleveland, Ohio;
authors: Gazanfar
authors: G
authors: Rahmathulla
authors: 5Cleveland Clinic, Cleveland, Ohio;
authors: Wendi A
authors: WA
authors: Evanoff
authors: 3University of Pennsylvania, Philadelphia, Pennsylvania;
authors: Michelle
authors: M
authors: Alonso-Basanta
authors: 2University of Pittsburgh, Pennsylvania;
authors: L Dade
authors: LD
authors: Lunsford
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003388:Cranial Fossa, Posterior / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008579:Meningioma / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation*; D012737:Sex Factors; D019292:Skull Base Neoplasms / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult
keywords: CI = confidence interval; CN = cranial nerve; CPA = cerebellopontine angle; GKRS = Gamma Knife radiosurgery; Gamma Knife surgery; HR = hazard ratio; OR = odds ratio; SRS = stereotactic radiosurgery; meningioma; posterior fossa; stereotactic radiosurgery