title: Gamma knife radiosurgery for recurrent and residual meningeal hemangiopericytomas.
abstract: OBJECTIVE
  The aim of this study was to assess the clinical effects of Gamma Knife radiosurgery (GKS) for recurrent and residual meningeal hemangiopericytomas (M-HPC).
  
  
  METHODS
  Between December 1994 and December 2006, 22 patients with recurrent and residual M-HPC with 58 foci underwent GKS at the Gamma Knife Center of Beijing Neurosurgical Institute. Of these 22 patients, 13 patients (59.1%) were males and 9 patients (40.9%) were females. The mean age was 40.9 years (range 16-64 years). The mean volume of these tumors was 5.4 cm(3) (range 0.1-37.2 cm(3)). The mean tumor margin dose was 13.5 Gy (range 10.0-20.0 Gy). The mean tumor central dose was 28.2 Gy (range 21.8-35.0 Gy). The mean prescription isodose line was 48.4% (range 30.0-70.0%).
  
  
  RESULTS
  The mean period of follow-up was 26.0 months (range 5-90 months). Of these 22 patients, intracranial metastases developed in 7 patients (31.8%), extracranial metastases developed in 3 patients (13.6%). Four patients died. The mean life expectancy of these 22 patients was 67.7 months (range 7-192 months). Of these 58 foci, radiological follow-up showed that 25 foci (43.1%) nearly disappeared, 13 foci (22.4%) shrunk, 14 foci (24.1%) remained stable and 6 foci (10.3%) enlarged. The overall tumor control rate was 89.7%.
  
  
  CONCLUSIONS
  GKS provides an effective and safe adjunct management for postoperative small-to-moderate sized M-HPC and plays an important role in controlling recurrent and residual M-HPC to avoid a repeat surgical resection.
authors.affiliation: Gamma Knife Center, Beijing Neurosurgical Institute, Tiantan Hospital, Capital University of Medical Sciences, Beijing, China. ssbwyl@vip.sina.com
authors.forename: Shibin
authors.initials: S
authors.lastname: Sun
authors.forename: Ali
authors.initials: A
authors.lastname: Liu
authors.forename: Chongcheng
authors.initials: C
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*; D008579:Meningioma / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000601:surgery*; D018365:Neoplasm, Residual / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery; D015996:Survival Rate; D055815:Young Adult