Introduction: The role of bony fusion in influencing patient outcome and surgical revision rates in the treatment of metastatic spine disease is poorly defined. The goals of this study were, therefore, to evaluate the effect of fusion on revision surgery as well as on overall survival (OS) and functional status in patients with metastatic disease of the spine.
Methods: A retrospective cohort study of a prospective database at a major cancer center was conducted. A total of 25 patients who met the inclusion criteria from January 2010 to December 2015 were included. Functional status, patient and tumor characteristics, fusion status, and survival were analyzed, and regression analyses were done. Bony fusion was classified as either present (seen across a minimum of three levels and crossing the tumor site) or absent as evidenced through CT images at minimum of 1-year postoperatively.
Results: Twenty-five subjects with 28 surgical sites met the eligibility criteria to be included in this study cohort. Five surgical sites were found to have evidence of fusion on CT scans at 1 year after surgery, and 23 sites had no evidence of bridging fusion. No differences were found between the two groups in terms of OS, and ambulatory status (P > 0.10). Multivariate analysis did not reveal any specific factors affecting fusion. Mean follow-up was 23.7 months.
Discussion: The lack of bony fusion is not an independent predictor of the need for revision surgery. The lack of bony fusion in patients with metastatic disease of the spine does not appear to negatively affect their OS or their ambulatory status. A discussion of factors affecting fusion is complex, and there are other factors that may also play a role. Large multicenter trials are needed to corroborate the preliminary findings seen in this complex patient cohort.