How to select a treatment method for patients with potentially unstable metastatic vertebrae (spinal instability neoplastic score 7–12): a systematic review

The spinal instability neoplastic score (SINS) is used to evaluate spinal stability in patients with metastatic vertebrae and to guide treatment selection. SINSs of 13-18 indicate instability typically requiring surgery, while SINSs of 1-6 indicate stability and suitability for radiotherapy. However, the optimal approach for patients with SINSs of 7-12 remains unclear. This systematic review aimed to determine the optimal primary treatment for patients with intermediate SINSs (7-12) and potentially unstable metastatic vertebrae. A systematic literature search was conducted in PubMed, Embase, and Scopus, following the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines. Twenty-six studies were included in this review (three A-class and 23 B-class). The A-class studies showed better outcomes with surgery±radiotherapy than radiotherapy alone. Two B-class studies indicated that patients with SINSs ≥10 more frequently underwent surgery, and one study found surgery was less effective for SINSs ≤9. Four studies showed good outcomes of surgery. In another study, 30% of patients became unstable after radiotherapy. In four studies, vertebral compression fractures developed in 20%-30% of patients after stereotactic body radiation therapy or stereotactic ablative body radiotherapy. One study showed that SINSs of 7-12 were correlated with radiotherapy failure, while another study found no such association. This systematic review suggests that surgical intervention alone or in combination with radiation may be superior for patients with SINSs of 7-12 and metastatic spinal tumors. The SINS 7-12 category might be divided into subgroups where surgery or radiotherapy is optimal. SINS ≥10 may indicate a need for surgery, and individual SINS components could be predictive. Further research is warranted to obtain more definitive evidence.