Hardware failure in patients with metastatic cancer to the spine

Background The spine is the most common site of skeletal metastases, affecting approximately 30% of individuals with cancer. The aim of surgical treatment for metastatic spine disease is generally palliative to address pain and/or neurologic compromise, significantly improving patients’ quality of life. Patients with metastatic spine disease, however, represent a vulnerable cohort and may have comorbidities or previous treatments that impair the structural integrity of spinal hardware. As such, identifying factors that may contribute to hardware failure is an essential component in treating individuals with metastatic spine disease. Objective The aim of this study was to identify pre-operative risk factors associated with hardware failure in patients undergoing surgical treatment for metastatic spine disease. Methods A retrospective cohort study was conducted to include patients surgically treated for metastatic spine tumors between 2003 and 2013, at a single institution. A univariate analysis was initially performed to identify associated factors. Any associated factor with a p-value <0.20 was included in the multivariate analysis. Results 3 patients (1.9%), of the 159 patients included in the study, had failure of the spine instrumentation. 1 patient had metastatic prostate cancer, and 2 had metastatic breast cancer. Patient demographics, co-morbidities, tumor location, and primary tumor etiology were not found to be statistically significant, with respect to hardware failure. Predictive factors included in the multivariate model were other bone metastasis, visceral metastasis, brain metastasis, Modified Rankin scale, previous systemic chemotherapy, previous radiation to the spine, and mean survival. Previous radiation to the spine was the only factor to be significantly associated (p = 0.029), present in all three patients with hardware failure. Of note, there was a trend indicating that patients with longer life expectancies were more likely to experience hardware failure (mean survival of 16.7 months in non-failure cohort vs. 33 months in failure cohort), though this did not achieve statistical significance due to the limited sample size of patients with hardware failure. Conclusion Hardware failure is a risk for all patients who undergo instrumentation following resection for metastatic spine tumors. This study identified that pre-operative radiation may increase the risk for hardware failure in this population.