Study Design. Randomized clinical trial.
Objective. To determine if age affects outcomes from differing treatments in patients with spinal metastases.
Summary of Background Data. Recently, class I data were published supporting surgery with radiation over radiation alone for patients with malignant epidural spinal cord compression (MESCC). However, the criteria to properly select candidates for surgery remains controversial and few independent variables which predict success after treatment have been identified.
Methods. Data for this study was obtained in a randomized clinical trial comparing surgery versus radiation for MESCC. Hazard ratios were determined for the effect of age and the interaction between age and treatment. Age estimates at which prespecified relative risks could be expected were calculated with greater than 95% confidence to suggest possible age cut points for further stratification. Multivariate models and Kaplan-Meier curves were tested using stratified cohorts for both treatment groups in the randomized trial each divided into 2 age groups.
Results. Secondary data analysis with age stratification demonstrated a strong interaction between age and treatment (hazard ratio = 1.61, P = 0.01), such that as age increases, the chances of surgery being equal to radiation alone increases. The best estimate for the age at which surgery is no longer superior to radiation alone was calculated to be between 60 and 70 years of age (95% CI), using sequential prespecified relative risk ratios. Multivariate modeling and Kaplan-Meier curves for stratified treatment groups showed that there was no difference in outcome between treatments for patients ≥65 years of age. Ambulation preservation was significantly prolonged in patients <65 years of age undergoing surgery compared to radiation alone (P = 0.002).
Conclusion. Age is an important variable in predicting preservation of ambulation and survival for patiens being treated for spinal metastases. Our results provide compelling evidence for the first time that particular age cut points may help in selecting patients for surgical or nonsurgical intervention based on outcome.