Predictive Value of the Spinal Instability Neoplastic Score for Survival and Ambulatory Function After Surgery for Metastatic Spinal Cord Compression in 110 Patients with Prostate Cancer

STUDY DESIGN: We retrospectively analyzed Spinal Instability Neoplastic Score (SINS) in 110 patients with prostate cancer operated for metastatic spinal cord compression (MSCC). OBJECTIVE: We aimed to investigate the association between SINS and clinical outcomes after surgery for MSCC in patients with prostate cancer. SUMMARY OF BACKGROUND DATA: The SINS is a useful tool for assessing tumor-related spinal instability, but its prognostic value regarding survival and neurological outcome is still controversial. METHODS: We analyzed 110 consecutive patients with prostate cancer who underwent surgery for MSCC. The patients were categorized according to their SINS. Patients with castration-resistant prostate cancer (CRPC, n = 84) and those with hormone-naïve disease (n = 26) were analyzed separately. RESULTS: In total, 106 of 110 patients met the SINS criteria for potential instability or instability (scores 7-18). The median SINS was 10 (range 6-15) for patients with CRPC and 9 (7-16) for hormone-naïve patients. In the CRPC group, the SINS was classified as stable (score 0-6) in 4 patients, as potentially unstable (score 7-12) in 70 patients, and as unstable (score 13-18) in 10 patients. In the hormone-naïve group, 22 patients met the SINS criteria for potential instability and 4 patients for instability. There was no statistically significant difference in the overall risk for death between the SINS potentially unstable and unstable categories (adjusted hazard ratio 1.3, P = 0.4), or in the risk of loss of ambulation 1 month after surgery (adjusted odds ratio 1.4, P = 0.6). CONCLUSION: The SINS is helpful in assessing spinal instability when selecting patients for surgery, but it does not predict survival or neurological outcomes. Patients with a potential spinal instability benefit equally from surgery for MSCC as do patients with spinal instability.Level of Evidence: 3.