Validation of a score predicting post-treatment ambulatory status after radiotherapy for metastatic spinal cord compression

Purpose: A score predicting post-radiotherapy (RT) ambulatory status was developed based on 2,096 retrospectively evaluated metastatic spinal cord compression (MSCC) patients. This study aimed to validate the score in a prospective series. Methods and Materials: The score included five factors associated with post-RT ambulatory status: tumor type, interval tumor diagnosis to MSCC, visceral metastases, pre-RT motor function, time developing motor deficits. Patients were divided into five groups: 21-28, 29-31, 32-34, 35-37, 38-44 points. In this study, 653 prospectively followed patients were divided into the same groups. Furthermore, the number of prognostic groups was reduced from five to three (21-28, 29-37, 38-44 points). Post-RT ambulatory rates from this series were compared with the retrospective series. Additionally, this series was compared with 104 patients receiving decompressive surgery plus RT (41 laminectomy, 63 laminectomy plus stabilization of vertebrae). Results: In this study, post-RT ambulatory rates were 10.6% (21-28 points), 43.5% (29-31 points), 71.0% (32-34 points), 89.5% (35-37 points), and 98.5% (38-44 points). Ambulatory rates from the retrospective study were 6.2%, 43.5%, 70.0%, 86.1%, and 98.7%. After regrouping, ambulatory rates were 10.6% (21-28 points), 70.9% (29-37 points), and 98.5% (38-44 points) in this series, and 6.2%, 68.4%, and 98.7% in the retrospective series. Ambulatory rates were 0%, 62.5%, and 90.9% in the laminectomy plus RT group, and 14.3%, 83.9%, and 100% in the laminectomy + stabilization plus RT group. Conclusions: Ambulatory rates in the different groups in this study were similar to those in the retrospective study demonstrating the validity of the score. Using only three groups is simplier for clinical routine.