title: Re-irradiation stereotactic body radiotherapy for spinal metastases: a multi-institutional outcome analysis.
abstract: OBJECTIVE This study is a multi-institutional pooled analysis specific to imaging-based local control of spinal metastases in patients previously treated with conventional external beam radiation therapy (cEBRT) and then treated with re-irradiation stereotactic body radiotherapy (SBRT) to the spine as salvage therapy, the largest such study to date. METHODS The authors reviewed cases involving 215 patients with 247 spinal target volumes treated at 7 institutions. Overall survival was calculated on a patient basis, while local control was calculated based on the spinal target volume treated, both using the Kaplan-Meier method. Local control was defined as imaging-based progression within the SBRT target volume. Equivalent dose in 2-Gy fractions (EQD2) was calculated for the cEBRT and SBRT course using an α/β of 10 for tumor and 2 for both spinal cord and cauda equina. RESULTS The median total dose/number of fractions of the initial cEBRT was 30 Gy/10. The median SBRT total dose and number of fractions were 18 Gy and 1, respectively. Sixty percent of spinal target volumes were treated with single-fraction SBRT (median, 16.6 Gy and EQD2/10 = 36.8 Gy), and 40% with multiple-fraction SBRT (median 24 Gy in 3 fractions, EQD2/10 = 36 Gy). The median time interval from cEBRT to re-irradiation SBRT was 13.5 months, and the median duration of patient follow-up was 8.1 months. Kaplan-Meier estimates of 6- and 12-month overall survival rates were 64% and 48%, respectively; 13% of patients suffered a local failure, and the 6- and 12-month local control rates were 93% and 83%, respectively. Multivariate analysis identified Karnofsky Performance Status (KPS) < 70 as a significant prognostic factor for worse overall survival, and single-fraction SBRT as a significant predictive factor for better local control. There were no cases of radiation myelopathy, and the vertebral compression fracture rate was 4.5%. CONCLUSIONS Re-irradiation spine SBRT is effective in yielding imaging-based local control with a clinically acceptable safety profile. A randomized trial would be required to determine the optimal fractionation.
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, and.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hashmi
authors.affiliation: Department of Radiation Oncology, University of Wuerzburg, Germany;|Department of Radiation Oncology, University of Zurich, Zurich, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Guckenberger
authors.affiliation: Department of Radiation Oncology, Riverside Medical Center, Newport News, Virginia;
authors.forename: Ron
authors.initials: R
authors.lastname: Kersh
authors.affiliation: Departments of 5 Neurosurgery and.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Gerszten
authors.affiliation: Department of Radiation Oncology, University of Wuerzburg, Germany;
authors.forename: Frederick
authors.initials: F
authors.lastname: Mantel
authors.affiliation: Departments of 6 Radiation Oncology and.
authors.forename: Inga S
authors.initials: IS
authors.lastname: Grills
authors.affiliation: Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: John C
authors.initials: JC
authors.lastname: Flickinger
authors.affiliation: Departments of 8 Neurosurgery and.
authors.forename: John H
authors.initials: JH
authors.lastname: Shin
authors.affiliation: Neurosurgery, William Beaumont Hospital, Royal Oak, Michigan;
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Fahim
authors.affiliation: Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Brian
authors.initials: B
authors.lastname: Winey
authors.affiliation: Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Kevin
authors.initials: K
authors.lastname: Oh
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Center, University of Toronto, Ontario, Canada.
authors.forename: B C
authors.initials: BC
authors.lastname: John Cho
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Center, University of Toronto, Ontario, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Létourneau
authors.affiliation: Department of Neurosurgery, University of Virginia Health System, Charlottesville, Virginia; and.
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
authors.affiliation: Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, and.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D000069475:Re-Irradiation / Q000009:adverse effects / Q000379:methods*; D016879:Salvage Therapy / Q000009:adverse effects / Q000379:methods*; D013125:Spinal Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D013131:Spine / Q000601:surgery; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: CNT = critical neural tissue; Dmax = point maximum dose; EBRT = external beam radiation therapy; EQD2 = equivalent dose in 2-Gy fractions; ESSC = Elekta Spine Study Consortium; KPS = Karnofsky Performance Status; SBRT = stereotactic body radiotherapy; VCF = vertebral compression fracture; cEBRT = conventional EBRT; oncology; re-irradiation; salvage; spinal metastases; stereotactic body radiotherapy; stereotactic radiosurgery