Association between Opioid Requirement and Overall Survival in Patients with Spinal Metastases.

Introduction: Clinical evidence shows that opioid administration in cancer patients is associated with shorter survival. This study explored the impact of opioid requirement on overall survival of patients with spinal metastases. We also evaluated the association between opioid requirement and tumor-related spinal instability. Methods: We retrospectively identified 428 patients who had been diagnosed with spinal metastases from February 2009 to May 2017. Those with an opioid prescription during the first 1 month after the diagnosis were included in this study. Patients given opioids were divided into two groups: the opioid requirement group [≥5 mg oral morphine equivalent (OME)/day] and the nonopioid group (<5 mg OME/day). Spinal instability due to metastases was evaluated using the Spinal Instability Neoplastic Score (SINS). Cox proportional hazards analysis was performed to evaluate the relationship between opioid use and overall survival. Results: The most frequent primary cancer site was the lung, in 159 patients (37%), followed by the breast in 75 (18%) and the prostate in 46 (11%). Multivariate analyses showed that patients who required ≥5 mg OME/day were approximately twofold more likely to die after a spinal metastases diagnosis than those who required <5 mg OME/day (hazard ratio 2.13; 95% confidence interval 1.69-2.67; p<0.001). The SINS was significantly higher in the opioid requirement group than those in the nonopioid group (p<0.001). Conclusions: For patients with spinal metastases, opioid requirement was associated with shorter survival, independently of known prognostic factors. The patients were also more likely to have tumor-related spinal instability than those in the nonopioid group.