The Cost-Effectiveness of Surgical Intervention for Spinal Metastases: A Model-Based Evaluation

Operative and nonoperative treatments for spinal metastases are expensive interventions with a high rate of complications. We sought to determine the cost-effectiveness of a surgical procedure compared with nonoperative management as treatment for spinal metastases.

We constructed a Markov state-transition model with health states defined by ambulatory status and estimated the quality-adjusted life-years (QALYs) and costs for operative and nonoperative management of spine metastases. We considered 2 populations: 1 in which patients presented with independent ambulatory status and 1 in which patients presented with nonambulatory status due to acute (e.g., <48 hours) metastatic epidural compression. We defined the efficacy of each treatment as a likelihood of maintaining, or returning to, independent ambulation. Transition probabilities for the model, including the risks of mortality and becoming dependent or nonambulatory, were obtained from secondary data analysis and published literature. Costs were determined from Medicare reimbursement schedules. We conducted analyses over patients' remaining life expectancy from a health system perspective and discounted outcomes at 3% per year. We conducted sensitivity analyses to account for uncertainty in data inputs.

Among patients presenting as independently ambulatory, QALYs were 0.823 for operative treatment and 0.800 for nonoperative treatment. The incremental cost-effectiveness ratio (ICER) for a surgical procedure was $899,700 per QALY. Among patients presenting with nonambulatory status, those undergoing surgical intervention accumulated 0.813 lifetime QALY, and those treated nonoperatively accumulated 0.089 lifetime QALY. The incremental cost-effectiveness ratio for a surgical procedure was $48,600 per QALY. The cost-effectiveness of a surgical procedure was most sensitive to the variability of its efficacy.

Our data suggest that the value to society of a surgical procedure for spinal metastases varies according to the features of the patient population. In patients presenting as nonambulatory due to acute neurologic compromise, surgical intervention provides good value (ICER, $48,600 per QALY). There is a low value for a surgical procedure performed for patients who are ambulatory at presentation (ICER, $899,700 per QALY).

Economic and Decision Analysis Level III . See Instructions for Authors for a complete description of levels of evidence.