Treatment Strategies for Intermediate Spinal Instability Neoplastic Score Patients: A Systematic Review

Background: The Spinal Instability Neoplastic Score (SINS) is used in determining instability in patients with spinal metastases. Intermediate scores of 7 to 12 suggest possible instability, but there are no clear guidelines to address patients with these scores. Methods: We searched in PubMed, EMBASE, and Cochrane databases for studies that included patient demographics, tumor histology, surgical or radiotherapy management, and outcomes of patients with intermediate SINS. We reported mean differences and odds ratios (ORs) to assess differences between patients managed surgically versus with radiotherapy alone. Results: Thirteen articles, totaling 1822 patients with intermediate SINS were analyzed. In 5 studies (38.4%), the management decision was based on a tumor board review. There was no significant difference between surgical management versus radiotherapy (P = 0.24). When dichotomized into SINS 7–9 and 10–12, the OR for surgical management in the 10–12 group compared to the 7–9 group was 6.88 (95% confidence interval [CI] 2.31–20.5, P = 0.0005). More renal cell carcinomas were managed surgically instead of with radiotherapy alone than other tumor types (OR = 1.87, 95% CI = 1.14–3.05, P = 0.01). There was no statistical difference in overall complications between the 2 treatment groups (OR = 1.12, 95% CI = 0.49–2.54, P = 0.79). Vertebral fracture rates after any radiotherapy type ranged between 20% and 66%. The need for a surgical procedure, including stabilization, vertebroplasty, or kyphoplasty after radiotherapy ranged from 5% to 34.2%. Conclusions: Complication rates after surgery versus radiotherapy in the intermediate SINS category are similar, but the complication types differ. Patients in the 10–12 SINS subgroup, due to larger lytic area and higher probability of vertebral body fracture, could benefit from stabilization before radiotherapy.