Prognostic factors in patients with spinal metastasis: a systematic review and meta-analysis

Incidence of symptomatic spinal metastasis has increased owing to improvement in treatment of the disease. One of the key factors that influences decision-making is expected patient survival. To our knowledge, no systematic reviews or meta-analysis have been conducted that review independent prognostic factors in spinal metastases.

This study aimed to determine independent prognostic factors that affect outcome in patients with metastatic spine disease.

This is a systematic literature review and meta-analysis of publications for prognostic factors in spinal metastatic disease.

Pooled patient results from cohort and observational studies.

Meta-analysis for poor prognostic factors as determined by hazard ratio (HR) and 95% confidential interval (95% CI).

We systematically searched relevant publications in PubMed and Embase. The following search terms were used: ("'spinal metastases'" OR "'vertebral metastases'" OR ""spinal metastasis" OR 'vertebral metastases') AND ('"prognostic factors"' OR "'survival'"). Inclusion criteria were prospective and retrospective cohort series that report HR and 95% CI of independent prognostic factors from multivariate analysis. Two reviewers independently assessed all papers. The quality of included papers was assessed by using Newcastle-Ottawa Scale for cohort studies and publication bias was assessed by using funnel plot, Begg test, and Egger test. The prognostic factors that were mentioned in at least three publications were pooled. Meta-analysis was performed using HR and 95% CI as the primary outcomes of interest. Heterogeneity was assessed using the I² method.

A total of 3,959 abstracts (1,382 from PubMed and 2,577 from Embase) were identified through database search and 40 publications were identified through review of cited publications. The reviewers selected a total of 51 studies for qualitative synthesis and 43 studies for meta-analysis. Seventeen poor prognostic factors were identified. These included presence of a neurologic deficit before surgery, non-ambulatory status before radiotherapy (RT), non-ambulatory status before surgery, presence of bone metastases, presence of multiple bone metastases (>2 sites), presence of multiple spinal metastases (>3 sites), development of motor deficit in <7 days before initiating RT, development of motor deficit in <14 days before initiating RT, time interval from cancer diagnosis to RT <15 months, Karnofsky Performance Score (KPS) 10-40, KPS 50-70, KPS<70, Eastern Cooperative Oncology Group (ECOG) grade 3-4, male gender, presence of visceral metastases, moderate growth tumor on Tomita score (TS) classification, and rapid growth tumor on TS classification.

Seventeen independent poor prognostic factors were identified in this study. These can be categorized into cancer-specific and nonspecific prognostic factors. A tumor-based prognostic scoring system that combines all specific and general factors may enhance the accuracy of survival prediction in patients with metastatic spine disease.