Expanded Analysis of Vertebral Endplate Disruption and Its Impact on Vertebral Compression Fracture Risk

Background and Objectives: Vertebral compression fracture (VCF) is a potential serious complication of spinal stereotactic body radiotherapy (SBRT). Previously we noted a correlation between advanced Spinal Instability Neoplastic Score (SINS), tumor-related endplate (EP) disruption, and certain primary pathologies with increased VCF risk. Here, we report on an expanded patient cohort to further examine EP disruption's role in VCF. Methods: This retrospective cohort study was conducted at a single institution, gathering demographic and treatment data from patients who underwent spinal SBRT between 2013 and 2020. EP disruption was identified on pre-SBRT CT scans. Chronic steroid use was defined as steroids administered for 4 weeks or more. The 1-year cumulative incidence of VCF was evaluated by follow-up MRI and CT scans at 3-month intervals post-treatment. Based on multivariate analysis, a nomogram was created using four independent predictors: EP disruption, steroid use, SINS ≥7, and adverse histology. Results: A total of 173 patients were included. The median follow-up was 19 months. Approximately 69 patients (40%) had EP disruption. Thirty patients (17%) experienced a VCF at a median of 4.8 months from SBRT. Patients with adverse histology (HR 2.98, 95% CI [1.42-6.30], p .004), steroid use (HR 3.60, 95% CI [1.36-9.51], p .01), EP disruption (HR 4.16, 95% CI [1.57-11.05], p .004) and a SINS of ≥7 (HR 3.63, 95% CI [1.39-9.46], p .001) were associated with increased risk of VCF. Based on these findings, a nomogram was created with these four variables stratifying groups at low, intermediate, and high risk of VCF correlating with rates of 2%, 21% and 58% risk ( P < .001). Conclusion: In this expanded pooled analysis, consistent with previously published findings, EP disruption, adverse pathology, and higher SINS scores were associated with an increased risk of VCF. Additionally, we found that chronic steroid use for four weeks or greater also correlated with a higher risk of VCF.