2026 Development of a Modified Radiographic Spinal Instability Neoplastic Score (rSINS): Towards Earlier Referral and Management of Metastatic Spine Tumors

INTRODUCTION: The Spinal Instability Neoplastic Score (SINS) is an 18-point index used to identify patients with metastatic spinal tumors who may benefit from surgical referral. SINS categorizes patients according to stability using six variables: lesion location, lesion quality, spinal alignment, vertebral collapse, posterolateral element involvement, and mechanical pain. A modified SINS that can be evaluated on imaging could be used as a screening tool by radiologists to facilitate earlier referral, particularly for intermediate SINS (“potentially unstable”) cases. METHODS: Patients who underwent surgery for metastatic spinal tumor (2015–2022) were retrospectively included. SINS was evaluated for all cases. A 5-variable rSINS was evaluated without the pain variable. Concordance (% agreement) between SINS and rSINS and Kendall’s W coefficient were calculated to determine optimal rSINS thresholds for “potentially unstable” and “unstable.” Three- and two-variable SINS scores were also evaluated for comparison. RESULTS: Across 102 patients, mean SINS was 9.7 (range 2–17; 12.8% SINS 0-6, 68.6% SINS 7-12, 18.6% SINS 13-18). After optimization, rSINS thresholds of 0-4 (“stable”), 5-9 (“potentially unstable”), and 10-15 (“unstable”) demonstrated 95.1% concordance and similarity (p=0.016) with the original SINS. The resulting corresponding updated rSINS classification was 13.7% (0-4), 65.7% (5-9), and 20.6% (10-15). Overall, 94.2% (66/70) of SINS 7-12 patients remained in the “potentially unstable” category, with 2 total patients moving up a category and 2 moving down. A 2-variable rSINS (only alignment and vertebral collapse) had concordance of 74.5%, with optimized thresholds of 1-3 (“potentially unstable”) and 4-7 (“unstable”). A 3-variable SINS (re-including pain) identified 14/19 unstable patients (SINS 13-18) with a sensitivity of 73.7%. CONCLUSIONS: A 5-point modified version of SINS evaluable entirely from imaging had 95.1% concordance with the original 6-point SINS. Further reduced versions had weaker agreement.