title: Spot-scanning-based proton therapy for extracranial chordoma.
abstract: OBJECTIVE
  To evaluate effectiveness and safety of spot-scanning-based proton-radiotherapy (PT) for extracranial chordomas (ECC).
  
  
  METHODS
  Between 1999-2006, 40 patients with chordoma of C-, T-, and L-spine and sacrum were treated at Paul Scherrer Institute (PSI) with PT using spot-scanning. Median patient age was 58 years (range, 10-81 years); 63% were male, and 36% were female. Nineteen patients (47%) had gross residual disease (mean 69 cc; range, 13-495 cc) before PT, and 21 patients (53%) had undergone prior titanium-based surgical stabilization (SS) and reconstruction of the axial skeleton. Proton doses were expressed as Gy(RBE). A conversion factor of 1.1 was used to account for higher relative biological effectiveness (RBE) of protons compared with photons. Mean total dose was 72.5 Gy(RBE) [range, 59.4-75.2 Gy(RBE)] delivered at 1.8-2.0 Gy(RBE) dose per fraction. Median follow-up time was 43 months.
  
  
  RESULTS
  In 19 patients without surgical stabilization, actuarial local control (LC) rate at 5 years was 100%. LC for patients with gross residual disease but without surgical stabilization was also 100% at 5 years. In contrast, 12 failures occurred in 21 patients with SS, yielding a significantly decreased 5-year LC rate of 30% (p = 0.0003). For the entire cohort, 5-year LC rates were 62%, disease-free survival rates were 57%, and overall survival rates were 80%. Rates were 100% for patients without SS. No other factor, including dosimetric parameters (V95, V80) were predictive for tumor control on univariate analysis.
  
  
  CONCLUSIONS
  Spot-scanning-based PT at PSI delivered subsequently to function-preserving surgery for tumor debulking, decompression of spinal cord, or biopsy only is safe and highly effective in patients with ECC without major surgical instrumentation even in view of large, unresectable disease.
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland. adrian.staab@psi.ch
authors.forename: Adrian
authors.initials: A
authors.lastname: Staab
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Rutz
authors.forename: Carmen
authors.initials: C
authors.lastname: Ares
authors.forename: Beate
authors.initials: B
authors.lastname: Timmermann
authors.forename: Ralf
authors.initials: R
authors.lastname: Schneider
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bolsi
authors.forename: Francesca
authors.initials: F
authors.lastname: Albertini
authors.forename: Antony
authors.initials: A
authors.lastname: Lomax
authors.forename: Gudrun
authors.initials: G
authors.lastname: Goitein
authors.forename: Eugen
authors.initials: E
authors.lastname: Hug
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002817:Chordoma / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D061766:Proton Therapy; D011522:Protons / Q000009:adverse effects; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods; D012062:Relative Biological Effectiveness; D013125:Spinal Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D016019:Survival Analysis; D017211:Treatment Failure; D047368:Tumor Burden
chemical_list: D011522:Protons