Spine Instability Neoplastic Score: agreement across different medical and surgical specialties

Background Context Spinal instability is an acknowledged complication of spinal metastases; in spite of recent suggested criteria, it is not clearly defined in the literature. Purpose This study aimed to assess intra and interobserver agreement when using the Spine Instability Neoplastic Score (SINS) by all physicians involved in its management. Study Design Independent multicenter reliability study for the recently created SINS, undertaken with a panel of medical oncologists, neurosurgeons, radiologists, orthopedic surgeons, and radiation oncologists, was carried out. Patient Sample Ninety patients with biopsy-proven spinal metastases and magnetic resonance imaging, reviewed at the multidisciplinary tumor board of our institution, were included. Outcome Measures Intraclass correlation coefficient (ICC) was used for SINS score agreement. Fleiss kappa statistic was used to assess agreement on the location of the most affected vertebral level; agreement on the SINS category ("stable," "potentially stable," or "unstable"); and overall agreement with the classification established by tumor board. Methods Clinical data and imaging were provided to 83 specialists in 44 hospitals across 14 Spanish regions. No assessment criteria were pre-established. Each clinician assessed the SINS score twice, with a minimum 6-week interval. Clinicians were blinded to assessments made by other specialists and to their own previous assessment. Subgroup analyses were performed by clinicians' specialty, experience (≤7, 8–13, ≥14 years), and hospital category (four levels according to size and complexity). This study was supported by Kovacs Foundation. Results Intra and interobserver agreement on the location of the most affected levels was "almost perfect" (κ>0.94). Intra-observer agreement on the SINS score was "excellent" (ICC=0.77), whereas interobserver agreement was "moderate" (ICC=0.55). Intra-observer agreement in SINS category was "substantial" (k=0.61), whereas interobserver agreement was "moderate" (k=0.42). Overall agreement with the tumor board classification was "substantial" (κ=0.61). Results were similar across specialties, years of experience, and hospital category. Conclusions Agreement on the assessment of metastatic spine instability is moderate. The SINS can help improve communication among clinicians in oncology care.