title: Gamma Knife surgery for skull base chordomas and chondrosarcomas.
abstract: OBJECTIVE
  The purpose of this study was to evaluate radiosurgical outcomes in skull base chordomas and chondrosarcomas, and to determine which tumors are appropriate for stereotactic radiosurgery as adjuvant therapy following maximum tumor resection.
  
  
  METHODS
  Thirty-seven patients (48 lesions) were treated using Gamma Knife surgery (GKS); 27 had chordomas, seven had chondrosarcomas, and three had radiologically diagnosed chordomas. The mean tumor volume was 20 ml, and the mean maximum and marginal doses were 28 and 14 Gy, respectively. The mean follow-up period was 97 months from diagnosis and 59 months from GKS.
  
  
  RESULTS
  The actuarial 5- and 10-year survival rates after GKS were 80 and 53%, respectively. The actuarial 5- and 10-year local tumor control (LTC) rates after single or multiple GKS sessions were 76 and 67%, respectively. All patients with low-grade chondrosarcomas achieved good LTC. A tumor volume of less than 20 ml significantly affected the high rate of LTC (p = 0.0182). No patient had adverse radiation effects, other than one in whom facial numbness worsened despite successful tumor control.
  
  
  CONCLUSIONS
  As an adjuvant treatment after resection, GKS is a reasonable option for selected patients harboring skull base chordomas or chondrosarcomas with a residual tumor volume of less than 20 ml. Dose planning with a generous treatment volume to avoid marginal treatment failure should be made at a marginal dose of at least 15 Gy to achieve long-term tumor control.
authors.affiliation: Department of Neurosurgery, Gamma Knife Center, Komaki City Hospital, Komaki, Japan. h-toshi@komakihp.gr.jp
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Dai
authors.initials: D
authors.lastname: Ishii
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kida
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: Joji
authors.initials: J
authors.lastname: Koike
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iizuka
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002813:Chondrosarcoma / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D002817:Chordoma / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011829:Radiation Dosage; D016634:Radiosurgery / Q000401:mortality*; D019292:Skull Base Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D015996:Survival Rate