title: Results of spot-scanning proton radiation therapy for chordoma and chondrosarcoma of the skull base: the Paul Scherrer Institut experience.
abstract: OBJECTIVE
  To assess the clinical results of spot scanning proton beam radiation therapy (PT) in the treatment of skull base chordomas and low-grade chondrosarcomas (CS).
  
  
  METHODS
  Between October 1998 and October 2003, 29 patients (median age, 39 years) with chordomas (n = 18) and CS (n = 11) were treated at the Paul Scherrer Institut (PSI) with protons using the main 510-MeV cyclotron. Tumor conformal application of proton beams was realized by spot scanning technology. The median chordoma and CS dose was 74 and 68 cobalt Gy equivalent, respectively (cobalt Gy equivalent = proton Gy x 1.1). Median gross tumor volumes (GTV) were 16.4 mL (range, 1.8-48.1 mL) and 15.2 mL (range, 2.3-57.3 mL) for chordoma and CS, respectively. Late toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE, v3.0) grading system. The median follow-up time was 29 months (range, 6-68 months).
  
  
  RESULTS
  Actuarial 3-year local control rates were 87.5% and 100% for chordoma and CS, respectively. We observed one surgical pathway and one marginal failure in patients with chordomas. No regional failure or distant metastasis was observed. At 3 years, actuarial PFS and OS for the entire cohort was 90% and 93.8%, respectively. Actuarial 3-year complication-free survival was 82.2%. Radiation-induced pituitary dysfunction was observed in 4 (14%) patients (CTCAE Grade 2). No patient presented with post-PT brainstem or optic pathways necrosis or dysfunction. In univariate analysis, age < or =40 years at the time of PT affected favorably on PFS (p = 0.09).
  
  
  CONCLUSIONS
  Spot-scanning PT offers high tumor control rates of skull base chordoma and CS. These results compare favorably to other combined proton-photon or carbon ion irradiation series. Observed toxicity was acceptable. Younger age (< or =40 years) was a favorable prognostic factor of PFS. These preliminary results are encouraging but should be confirmed during a longer follow-up.
authors.affiliation: Department of Radiation Medicine, Proton Therapy Program, Paul Scherrer Institut, Villigen, Switzerland. damien.weber@hcuge.ch
authors.forename: Damien C
authors.initials: DC
authors.lastname: Weber
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Rutz
authors.forename: Eros S
authors.initials: ES
authors.lastname: Pedroni
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bolsi
authors.forename: Beate
authors.initials: B
authors.lastname: Timmermann
authors.forename: Jorn
authors.initials: J
authors.lastname: Verwey
authors.forename: Antony J
authors.initials: AJ
authors.lastname: Lomax
authors.forename: Gudrun
authors.initials: G
authors.lastname: Goitein
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002813:Chondrosarcoma / Q000532:radiotherapy*; D002817:Chordoma / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D019292:Skull Base Neoplasms / Q000532:radiotherapy*; D016896:Treatment Outcome; D011522:Protons
chemical_list: D011522:Protons