Clinical Evaluation of the Spinal Instability Neoplastic Score in Patients Treated With Radiotherapy for Symptomatic Spinal Bone Metastases

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To determine the predictive value of the Spinal Instability Neoplastic Score (SINS) in a cohort of patients treated with radiotherapy for spinal bone metastases. SUMMARY OF BACKGROUND DATA: Assessment of spinal stability in metastatic disease is challenging and is mostly done by relying on clinical experience, in the absence of validated guidelines or an established predetermined set of risk factors. The SINS provides clinicians with a tool to assess tumor-related spinal instability. METHODS: A total of 110 patients were included in this retrospective study. Time to event was calculated as the difference between start of radiotherapy and date of occurrence of an adverse event or last follow-up, with death being considered a competing event. A competing risk analysis was performed to estimate the effect of the SINS on the cumulative incidence of the occurrence of an adverse event. RESULTS: Sixteen patients (15%) experienced an adverse event during follow-up. The cumulative incidence for the occurrence of an adverse event at 6 and 12 months was 11.8% (95% confidence interval 5.1%-24.0%) and 14.5% (95% confidence interval 6.9%-22.2%), respectively. Competing risk analysis showed that the final SINS classification was not significantly associated with the cumulative incidence of an adverse event within the studied population. CONCLUSION: The clinical applicability of the SINS as a tool to assess spinal instability seems limited. LEVEL OF EVIDENCE: 3.