Clinical Outcomes After Spine Surgery for Patients with Potentially Unstable Metastatic Spinal Disease (Spine Instability Neoplastic Score 7-12): A Systematic Review.

Abstract

While the surgical management of metastatic spinal disease has wide consensus for "stable" (Spine Instability Neoplastic Score [SINS] 0-6) and "unstable" (SINS 13-18) disease, there is limited consensus regarding spine surgery for patients with "potentially unstable" (SINS 7-12) metastatic disease. We examined the clinical outcomes for these patients after spine surgery. This systematic review examined articles from PubMed, CINAHL, MEDLINE, and Web of Science from database inception until December 18th, 2024. Inclusion criteria were studies that examined clinical outcomes in patients with SINS 7-12 who underwent spine surgery. Among 111 articles, 10 observational studies were included. Of 1546 patients, 942 with SINS 7-12 underwent spine surgery for metastases. Average postoperative survival ranged from 10-14 months, with an 80% 6-month survival and 59% 1-year survival. One article found a statistically significant survival benefit with surgery over radiation, while 2 did not. Patients with SINS 10-12 were more likely to receive instrumentation than SINS 7-9. Surgery may be more effective than radiation for patient-reported outcomes. Rates of subsequent spine surgery after nonsurgical treatments ranged from 4.0% to 25.5%. Indications for instrumentation may include osteolytic lesions and >50% vertebral body collapse with no consistency between articles. Cutoff scores of SINS 9 or 10 were associated with the decision to use instrumentation. Patients with potentially unstable metastatic spinal disease (SINS 7-12) treated with surgery have varying survival rates and outcomes in comparison to radiation. Up to 25% of patients with SINS 7-12 may fail nonoperative treatments. SINS 7-12 represents heterogeneous grouping of spine instability, with possible subgroups within SINS 7-12.