title: Treatment of chordomas with CyberKnife: georgetown university experience and treatment recommendations.
abstract: OBJECTIVE
  To determine the efficacy and safety of chordoma treatment with CyberKnife (Accuray, Inc., Sunnyvale, CA) stereotactic radiosurgery (CK/SRS).
  
  
  METHODS
  Eighteen patients with chordoma were treated with CK/SRS as a primary adjuvant (17 patients) or the only treatment (1 patient). The series included 24 lesions (28 treatments). The median age of the patients was 60 years (range, 24-85 years). Forty-four percent of the tumors were located in the mobile spine, 39% inside the cranium, and 17% in the sacral region. The male-to-female ratio was 1:1. The mean tumor volume was 128.0 mL (range, 12.0-457.3 mL), and the median dose of 35 Gy (range, 24.0-40.0 Gy) was delivered in 5 sessions. The median follow-up period was 46 months (range, 7-65 months).
  
  
  RESULTS
  There were 3 significant complications in patients with previous irradiation, including infection in the surgical/radiation site (2 patients) and decreased vision (1 patient). Improvement in pain and quality of life did not reach statistical significance (alpha = 0.05). Seven patients experienced recurrence at a median of 10 months (range, 5-38 months), and 4 patients with disseminated disease died 7 to 48 months after therapy. Two patients had a partial response, whereas 9 others had stable disease. The local control rate at 65 months was 59.1%, with an overall survival of 74.3% and disease-specific survival of 88.9%. We estimated an alpha/beta ratio of 2.45 for chordomas, which supports hypofractionation.
  
  
  CONCLUSIONS
  The CK/SRS safety and efficacy profile compares favorably with those of other treatment delivery systems. CK/SRS appears to reduce tumor volume, given an adequate dose. The authors recommend treatment with 40 Gy in 5 sessions to the clinical treatment volume, which includes the gross tumor volume and at least a 1-cm margin.
authors.affiliation: Department of Radiology, Georgetown University, Washington, District of Columbia 20007, USA. henderson@fraserhendersonmd.com
authors.forename: Fraser C
authors.initials: FC
authors.lastname: Henderson
authors.forename: Kyle
authors.initials: K
authors.lastname: McCool
authors.forename: Juliet
authors.initials: J
authors.lastname: Seigle
authors.forename: Walter
authors.initials: W
authors.lastname: Jean
authors.forename: William
authors.initials: W
authors.lastname: Harter
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gagnon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016543:Central Nervous System Neoplasms / Q000401:mortality / Q000601:surgery*; D002817:Chordoma / Q000401:mortality / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000601:surgery; D011183:Postoperative Complications; D011788:Quality of Life; D016634:Radiosurgery / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D016896:Treatment Outcome; D014495:Universities