title: Updated Outcome and Analysis of Tumor Response in Mobile Spine and Sacral Chordoma Treated With Definitive High-Dose Photon/Proton Radiation Therapy.
abstract: Treatment of spine and sacral chordoma generally involves surgical resection, usually in conjunction with radiation therapy. In certain circumstances where resection may result in significant neurologic or organ dysfunction, patients can be treated definitively with radiation therapy alone. Herein, we report the outcome and the assessment of tumor response to definitive radiation therapy.
  
  
  
  A retrospective analysis was performed on 40 patients with unresected chordoma treated with photon/proton radiation therapy. Nineteen patients had complete sets of imaging scans. The soft tissue and bone compartments of the tumor were defined separately. Tumor response was evaluated by the modified Response Evaluation Criteria in Solid Tumors (RECIST) and volumetric analysis.
  
  
  
  With a median follow-up time of 50.3 months, the rates of 5-year local control, overall survival, disease-specific survival, and distant failure were 85.4%, 81.9%, 89.4%, and 20.2%, respectively. Eighty-four computed tomographic and magnetic resonance imaging scans were reviewed. Among the 19 patients, only 4 local failures occurred, and the median tumor dose was 77.4 GyRBE. Analysis at a median follow-up time of 18 months showed significant volumetric reduction of the total target volume (TTV) and the soft tissue target volume (STTV) within the first 24 months after treatment initiation, followed by further gradual reduction throughout the rest of the follow-up period. The median maximum percentage volumetric regressions of TTV and STTV were 43.2% and 70.4%, respectively. There was only a small reduction in bone target volume over time. In comparison with the modified RECIST, volumetric analysis was more reliable, more reproducible, and could help in measuring minimal changes in the tumor volume.
  
  
  
  These results continue to support the use of high-dose definitive radiation therapy for selected patients with unresected spine and sacral chordomas. Assessment of tumor response to radiation therapy by volumetric analysis is superior to modified RECIST in chordoma patients. Evaluating the soft tissue target volume is an excellent indicator of tumor response.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. Electronic address: peyman.kabolizadeh@beaumont.org.
authors.forename: Peyman
authors.initials: P
authors.lastname: Kabolizadeh
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Yen-Lin
authors.initials: YL
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Norbert
authors.initials: N
authors.lastname: Liebsch
authors.affiliation: Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Hornicek
authors.affiliation: Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Schwab
authors.affiliation: Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Edwin
authors.initials: E
authors.lastname: Choy
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Rosenthal
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Niemierko
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: DeLaney
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002817:Chordoma / Q000000981:diagnostic imaging / Q000401:mortality / Q000532:radiotherapy*; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use*; D061766:Proton Therapy / Q000009:adverse effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012044:Regression Analysis; D066066:Response Evaluation Criteria in Solid Tumors; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000401:mortality / Q000532:radiotherapy*; D013997:Time Factors; D014057:Tomography, X-Ray Computed