title: Outcomes for Spine Stereotactic Body Radiation Therapy and an Analysis of Predictors of Local Recurrence.
abstract: OBJECTIVE
  To investigate local control, survival outcomes, and predictors of local relapse for patients treated with spine stereotactic body radiation therapy.
  
  
  METHODS
  We reviewed the records of 332 spinal metastases consecutively treated with stereotactic body radiation therapy between 2002 and 2012. The median follow-up for all living patients was 33 months (range, 0-111 months). Endpoints were overall survival and local control (LC); recurrences were classified as either in-field or marginal.
  
  
  RESULTS
  The 1-year actuarial LC and overall survival rates were 88% and 64%, respectively. Patients with local relapses had poorer dosimetric coverage of the gross tumor volume (GTV) compared with patients without recurrence (minimum dose [Dmin] biologically equivalent dose [BED] 23.9 vs 35.1 Gy, P<.001; D98 BED 41.8 vs 48.1 Gy, P=.001; D95 BED 47.2 vs 50.5 Gy, P=.004). Furthermore, patients with marginal recurrences had poorer prescription coverage of the GTV (86% vs 93%, P=.01) compared with those with in-field recurrences, potentially because of more upfront spinal canal disease (78% vs 24%, P=.001). Using a Cox regression univariate analysis, patients with a GTV BED Dmin ≥33.4 Gy (median dose) (equivalent to 14 Gy in 1 fraction) had a significantly higher 1-year LC rate (94% vs 80%, P=.001) compared with patients with a lower GTV BED Dmin; this factor was the only significant variable on multivariate Cox analysis associated with LC (P=.001, hazard ratio 0.29, 95% confidence interval 0.14-0.60) and also was the only variable significant in a separate competing risk multivariate model (P=.001, hazard ratio 0.30, 95% confidence interval 0.15-0.62).
  
  
  CONCLUSIONS
  Stereotactic body radiation therapy offers durable control for spinal metastases, but there is a subset of patients that recur locally. Patients with local relapse had significantly poorer tumor coverage, which was likely attributable to treatment planning directives that prioritized the spinal cord constraints over tumor coverage. When possible, we recommend maintaining a GTV Dmin above 14 Gy in 1 fraction and 21 Gy in 3 fractions.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Bishop
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Randa
authors.initials: R
authors.lastname: Tao
authors.affiliation: Department of Radiation Dosimetry, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Neal C
authors.initials: NC
authors.lastname: Rebueno
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Eva N
authors.initials: EN
authors.lastname: Christensen
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Allen
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Xin A
authors.initials: XA
authors.lastname: Wang
authors.affiliation: Department of Diagnostic Radiology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Behrang
authors.initials: B
authors.lastname: Amini
authors.affiliation: Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Nizar M
authors.initials: NM
authors.lastname: Tannir
authors.affiliation: Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Claudio E
authors.initials: CE
authors.lastname: Tatsui
authors.affiliation: Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Rhines
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, USC Norris Cancer Hospital, Keck School of Medicine of USC, Los Angeles, California.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Brown
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: ajghia@mdanderson.org.
authors.forename: Amol J
authors.initials: AJ
authors.lastname: Ghia
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000601:surgery*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D013125:Spinal Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D015996:Survival Rate; D017211:Treatment Failure; D055815:Young Adult