title: Radiosurgery for intracranial hemangiopericytomas: outcomes after initial and repeat Gamma Knife surgery.
abstract: OBJECTIVE
  Intracranial hemangiopericytoma is a rare CNS tumor that exhibits a high incidence of local recurrence and distant metastasis. The purpose of this study was to evaluate the role of Gamma Knife surgery (GKS) in the management of intracranial hemangiopericytomas.
  
  
  METHODS
  In a review of the University of Virginia radiosurgery database between 1989 and 2008, the authors found recurrent or residual hemangiopericytomas after resection in 21 patients in whom radiosurgery was performed to treat 28 discrete tumors. The median age of this population was 47 years (range 31-61 years) at the time of the initial GKS. Prior treatments included embolization (6), transcranial resection (39), transsphenoidal resection (2), and fractionated radiotherapy (8). The mean prescription and maximum radiosurgical doses to the tumors were 17.0 and 40.3 Gy, respectively. Repeat radiosurgery was used to treat 13 tumors. The median follow-up period was 68 months (range 2-138 months).
  
  
  RESULTS
  At last follow-up, local tumor control was demonstrated in 47.6% of the patients (10 of 21 patients) with hemangiopericytomas. Of the 28 tumors treated, 8 decreased in size on follow-up imaging (28.6%), 5 remained unchanged (17.9%), and 15 ultimately progressed (53.6%). The progression-free survival rates were 90, 60.3, and 28.7% at 1, 3, and 5 years after initial GKS. The progression-free survival rate improved to 95, 71.5, and 71.5% at 1, 3, and 5 years after multiple GKS treatments. The 5-year survival rate after radiosurgery was 81%. Prior fractionated irradiation or radiosurgical prescription dose did not correlate with tumor control. In 4 (19%) of 21 patients extracranial metastases developed.
  
  
  CONCLUSIONS
  Radiosurgery is a reasonable treatment option for recurrent hemangiopericytomas. Long-term close clinical and imaging follow-up is necessary because of the high probability of local recurrence and distant metastases. Repeat radiosurgery may be used to treat new or recurrent hemangiopericytomas over a long follow-up course.
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
authors.forename: Claire
authors.initials: C
authors.lastname: Olson
authors.forename: Chun-Po
authors.initials: CP
authors.lastname: Yen
authors.forename: David
authors.initials: D
authors.lastname: Schlesinger
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000473:pathology / Q000601:surgery* / Q000628:therapy; D003399:Craniotomy / Q000379:methods; D018450:Disease Progression; D004621:Embolization, Therapeutic; D005260:Female; D005500:Follow-Up Studies; D006393:Hemangiopericytoma / Q000473:pathology / Q000601:surgery* / Q000628:therapy; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D013100:Sphenoid Bone / Q000601:surgery; D016896:Treatment Outcome