title: Marginal recurrence requiring salvage radiotherapy after stereotactic body radiotherapy for spinal metastases.
abstract: BACKGROUND
  We sought to quantify and identify risk factors associated with margin recurrence (MR) requiring salvage radiotherapy after stereotactic body radiation therapy (SBRT) for spinal metastases.
  
  
  METHODS
  We retrospectively reviewed patients with spinal metastases who were treated with single-fraction SBRT between 2006 and 2009. Gross tumor was contoured, along with either the entire associated vertebral body(ies) or the posterior elements, and included in the planning target volume. No additional margins were used. MR was defined as recurrent tumor within one vertebral level above or below the treated lesion that required salvage radiotherapy. Only patients who presented for 3-month post-SBRT follow-up were included in the analysis. Fine and Gray competing risk regression models were generated to identify variables associated with higher risks of MR. MR was plotted using cumulative incidence analysis.
  
  
  RESULTS
  SBRT was delivered to 208 lesions in 149 patients. Median follow-up was 8.6 months, and median survival was 12.8 months. The median prescribed dose was 14 Gy (10-16 Gy). MR occurred in 26 (12.5%) treated lesions, at a median time of 7.7 months after SBRT. Patients with paraspinal disease at the time of SBRT (20.8% vs. 7.6% of patients; p = 0.02), and those treated with <16 Gy (16.3% vs. 6.3% of patients, p = 0.14) had higher rates of MR. Both variables were associated with significantly higher risk of MR on multivariate analysis.
  
  
  CONCLUSIONS
  SBRT for spinal metastases results in a low overall rate of MR. The presence of paraspinal disease at the time of SBRT and a dose of <16 Gy were associated with higher risks of MR.
authors: Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio, USA.
authors: Shlomo A
authors: SA
authors: Koyfman
authors: Toufik
authors: T
authors: Djemil
authors: Michael J
authors: MJ
authors: Burdick
authors: Neil
authors: N
authors: Woody
authors: Ehsan H
authors: EH
authors: Balagamwala
authors: Chandana A
authors: CA
authors: Reddy
authors: Lilyana
authors: L
authors: Angelov
authors: John H
authors: JH
authors: Suh
authors: Samuel T
authors: ST
authors: Chao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002648:Child; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy*; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012189:Retrospective Studies; D012307:Risk Factors; D016879:Salvage Therapy / Q000379:methods*; D013125:Spinal Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery*; D047368:Tumor Burden; D055815:Young Adult