The Oswestry Spinal Risk Index (OSRI) in assessing prognosis of patients with spinal metastases

Abstract

Introduction: The Oswestry Spinal Risk Index (OSRI) was designed to predict life expectancy of patients presenting with spinal metastases. It integrates the most predictive items of existing scores and is calculated using not more than two items: General condition and primary tumor. Research question: The purpose of this study was to externally validate the OSRI in a large cohort and to compare it with the established scores. Material and methods: We retrospectively identified 211 consecutive surgical patients with symptomatic spinal metastases. We collected clinical and radiographic data, such as Karnofsky Performance Score (KPS), Frankel Status, primary tumor pathology and metastatic spread to calculate the Tokuhashi score, Tomita score, modified Bauer score and the OSRI. Logistic regression models, Kaplan-Meyer-curves, discriminant power and variance analyses were applied using Harrell’s C-index and Cox and Snell’s Pseudo R². Results: Predicted and actual survival of our cohort’s patients correlated significantly in each investigated scoring systems (p < 0.001). In test quality measurements Tokuhashi score performed best (C = 0.7204; R² = 0.3619), followed by OSRI (C = 0.7023; R² = 0.2612), Tomita (C = 0.6748; R² = 0.2818) and modified Bauer score (C = 0.6653; R² = 0.2486). Accuracy of predicted life expectancy was highest in modified Bauer score and OSRI. Discussion and conclusion: Compared to the original scores, the OSRI provided equal or even superior results in assessing our study population’s life expectancy. Its particular advantage lies in the simplicity of its application, which well meets the demands of surgical decision-making in daily practice.

Keywords

• Oswestry spinal risk index
• Tokuhashi score
• Tomita score
• Modified Bauer score
• Spinal metastases
• Prognosis