Validation of the prognostic index for spine metastasis (PRISM) for stratifying survival in patients treated with spinal stereotactic body radiation

•The PRISM criteria uses patient characteristics to stratify patient prognosis following SSRS treatment.•PRISM can stratify OS in patients with diverse histologies and disease presentations from different treatment centers.•This scoring system may serve as a guide to selecting patients who would be most optimal for SSRS. The Prognostic Index for Spinal Metastasis (PRISM) is a scoring system derived from prospective data from a single institution that stratifies patients undergoing spine stereotactic radiosurgery (SSRS) for spinal metastases into subgroups by overall (OS). We sought to further demonstrate its generalizability by performing validation with a large dataset from a second high-volume institution, Mayo Clinic. Eight hundred seventy-nine patients—424 from Mayo Clinic and 455 from MD Anderson Cancer Center (MDACC)—who received SSRS between 2007 and 2019 were identified. Patients were stratified by PRISM criteria, and overall survival (OS) for the PRISM groups for each cohort was compared using Kaplan-Meier estimations and univariate Cox proportional analyses. Model calibration and concordance indices (C-indices) were calculated for each cohort to assess the quality of the scoring system. Patient and tumor characteristics varied significantly between both cohorts including histology, sex, performance status, and number of organs involved (all P