The Prognostic Impact of the Ki-67 Proliferation Index in Patients with Surgically Treated Spinal Metastases

Background: The prognostic assessment of patients with spinal metastases is primarily based on clinical and radiological parameters. Biological tumor characteristics such as the proliferation marker Ki-67 have prognostic relevance in various metastatic settings. This study aimed to evaluate the prognostic impact of the Ki-67 proliferation index on survival outcomes in patients undergoing surgery for spinal metastases. Methods: We included 166 patients who underwent surgical treatment for spinal metastases at our university clinic between 2015 and 2024. Clinical, functional, tumor-related, and perioperative variables were collected. Receiver operating characteristic (ROC) analysis was performed to evaluate the discriminatory ability of Ki-67, and comparisons were made between patient groups according to Ki-67 expression (≤20% vs. >20%). Results: Based on ROC analysis, Ki-67 demonstrated a moderate but significant predictive ability for 1-year mortality (area under the curve [AUC]: 0.69, p = 0.001). Patients with a Ki-67 index of >20% showed a significantly shorter overall survival than those with a lower Ki-67 index of ≤20% (median overall survival: 5.0 vs. 14.5 months, p < 0.001). One-year mortality was significantly higher in the high Ki-67 group (78.9% vs. 41.8%, p = 0.001). High Ki-67 expression was associated with more aggressive tumor characteristics but was not associated with increased perioperative morbidity. Conclusions: The Ki-67 proliferation index is a significant prognostic biomarker in surgically treated patients with spinal metastases. A Ki-67 index threshold of 20% identifies patients at increased risk of early mortality and significantly reduced overall survival.