Risk Factors for Vertebral Compression Fracture Following Spine Stereotactic Body Radiation Therapy

Vertebral compression fractures (VCFs) are potential complications following spine stereotactic body radiation therapy (SBRT). However, limited data exist on prognostic factors underlying VCF development following SBRT. The objective of this clinical cohort investigation was to evaluate risk factors for VCF development, VCF type (de novo or progressive), and VCF severity, following SBRT for spinal metastases.

A retrospective analysis was performed on a prospectively maintained database of 600 SBRT treatments (779 vertebral segments) for spinal metastases from 2002 to 2024. Exclusion criteria consisted of benign tumors, prior lesion-specific surgical intervention, and <1 month of follow-up. Logistic regression and Fine-Gray subdistribution hazard modeling was performed to evaluate predictors of VCF development.

The median follow-up was 8 months (range, 1-251 months). Fifty-seven (10%) VCFs were identified following SBRT: 29 (5%) de novo VCFs and 28 (5%) progressive VCFs. The median time-to-VCF was 6 months (range, 1-83 months). The 1- and 3-year cumulative incidence of VCF was 11% (95% CI, 8.1%-15%) and 21% (95% CI, 15%-27%), respectively. On multivariable analysis, female sex (odds ratio [OR], 1.06; 95% CI, 1.02-1.11; P = .007), lumbar lesions (OR, 1.05; 95% CI, 1.00-1.11; P = .049), and pre-existing VCF (OR, 1.01; 95% CI, 1.00-1.02; P = .009) were significantly associated with any VCF development, whereas a greater Spinal Instability Neoplastic Scores (SINS) at SBRT trended toward significance (OR, 1.07; 95% CI, 1.00-1.14; P = .060). Osteolytic disease (OR, 1.04; 95% CI, 1.00-1.07; P = .042) and epidural tumor extension (OR, 1.04; 95% CI, 1.01-1.07; P = .022) were associated with de novo VCF development, whereas only pre-existing VCF (OR, 1.08; 95% CI, 1.04-1.12; P < .001) was significantly associated with progressive VCF development. Thirty-three (58%) VCFs required subsequent surgical stabilization. On multivariable analysis, lumbar lesions (OR, 1.07; 95% CI, 1.02-1.12; P = .004), pre-existing VCF (OR, 1.07; 95% CI, 1.01-1.13; P = .026), and a greater SINS at SBRT (OR, 1.02; 95% CI, 1.01-1.02; P = .002) were significantly associated with VCFs requiring stabilization.

This large clinical cohort investigation successfully identified patient subgroups with increased risks of developing VCFs following spine SBRT for metastatic disease. Identifying these at-risk subpopulations may guide additional follow-up surveillance and consideration of individualized discussions regarding potential conservative or stabilization management approaches, particularly for those patients with multiple underlying risk factors.