Creation of a Prognostic Index for Spine Metastasis to Stratify Survival in Patients Treated With Spinal Stereotactic Radiosurgery: Secondary Analysis of Mature Prospective Trials.

Purpose There exists uncertainty in the prognosis of patients following spinal metastasis treatment. We sought to create a scoring system that stratifies patients based on overall survival. Methods and Materials Patients enrolled in 2 prospective trials investigating stereotactic spine radiation surgery (SSRS) for spinal metastasis with ≥3-year follow-up were analyzed. A multivariate Cox regression model was used to create a survival model. Pretreatment variables included were race, sex, age, performance status, tumor histology, extent of vertebrae involvement, previous therapy at the SSRS site, disease burden, and timing of diagnosis and metastasis. Four survival groups were generated based on the model-derived survival score. Results Median follow-up in the 206 patients included in this analysis was 70 months (range: 37-133 months). Seven variables were selected: female sex (hazard ratio [HR] = 0.7, P =.02), Karnofsky performance score (HR = 0.8 per 10-point increase above 60, P =.007), previous surgery at the SSRS site (HR = 0.7, P =.02), previous radiation at the SSRS site (HR = 1.8, P =.001), the SSRS site as the only site of metastatic disease (HR = 0.5, P =.01), number of organ systems involved outside of bone (HR = 1.4 per involved system, P 5 year interval from initial diagnosis to detection of spine metastasis (HR = 0.5, P P P Conclusions We developed the prognostic index for spinal metastases (PRISM) model, a new model that identified patient subgroups with poor and excellent prognoses.