title: Vertebral compression fractures after spine irradiation using conventional fractionation in patients with metastatic colorectal cancer.
abstract: OBJECTIVE
  To evaluate the risk of vertebral compression fracture (VCF) after conventional radiotherapy (RT) for colorectal cancer (CRC) with spine metastasis and to identify risk factors for VCF in metastatic and non-metastatic irradiated spines.
  
  
  METHODS
  We retrospectively reviewed 68 spinal segments in 16 patients who received conventional RT between 2009 and 2012. Fracture was defined as a newly developed VCF or progression of an existing fracture. The target volume included all metastatic spinal segments and one additional non-metastatic vertebra adjacent to the tumor-involved spines.
  
  
  RESULTS
  The median follow-up was 7.8 months. Among all 68 spinal segments, there were six fracture events (8.8%) including three new VCFs and three fracture progressions. Observed VCF rates in vertebral segments with prior irradiation or pre-existing compression fracture were 30.0% and 75.0% respectively, compared with 5.2% and 4.7% for segments without prior irradiation or pre-existing compression fracture, respectively (both p < 0.05). The 1-year fracture-free probability was 87.8% (95% CI, 78.2-97.4). On multivariate analysis, prior irradiation (HR, 7.30; 95% CI, 1.31-40.86) and pre-existing compression fracture (HR, 18.45; 95% CI, 3.42-99.52) were independent risk factors for VCF.
  
  
  CONCLUSIONS
  The incidence of VCF following conventional RT to the spine is not particularly high, regardless of metastatic tumor involvement. Spines that received irradiation and/or have pre-existing compression fracture before RT have an increased risk of VCF and require close observation.
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Woo Joong
authors.initials: WJ
authors.lastname: Rhee
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Jee Suk
authors.initials: JS
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Seohee
authors.initials: S
authors.lastname: Choi
authors.affiliation: Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University Health System, Seoul, Korea.
authors.forename: Woong Sub
authors.initials: WS
authors.lastname: Koom
keywords: Colorectal cancer; Compression fractures; Radiotherapy; Risk factors; Spinal fractures; Spinal neoplasm