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Cost-effectiveness analysis of single fraction of stereotactic body radiotherapy compared to single fraction of external beam radiotherapy for palliation of vertebral bone metastases.

26 Background: Stereotactic body radiotherapy (SBRT) has been proposed for the palliation of painful vertebral bone metastases because higher radiation doses may confer better pain control. A Phase III clinical trial comparing SBRT with single fraction external beam radiotherapy (EBRT) is now ongoing. We performed a cost-effectiveness analysis to compare these strategies.


METHODS
A Markov model, using a 1-month cycle over a lifetime horizon, was developed to compare the cost effectiveness of SBRT (16 or 18 Gy in 1 fraction) to 8 Gy in 1 fraction of EBRT. Transition probabilities, quality of life utilities, and costs associated with SBRT and EBRT were captured in the model. Costs were based on Medicare reimbursement in 2014. Strategies were compared using the incremental cost effectiveness ratio (ICER), and effectiveness was measured in quality-adjusted life years (QALYs). To account for uncertainty, one-way and probabilistic sensitivity analyses were performed. Strategies were evaluated with a willingness-to-pay (WTP) threshold of $100,000/QALY gained.


RESULTS
Base case pain relief after the treatment was assumed as 20% higher in SBRT. Treatment costs for SBRT and EBRT were $9000 and $1087, respectively. In the base case analysis, SBRT resulted in an ICER of $124,552/QALY gained. In one-way sensitivity analyses, results were most sensitive to variation of the utility of unrelieved pain (range: $89,330 to $592,720/QALY gained); the utility of relieved pain post-treatment and median survival were also sensitive to variation. If median survival is ≥11 months (base case estimate: 9 months), SBRT cost <$100,000/QALY gained. Probabilistic sensitivity analysis demonstrated that SBRT was favored in 30% of model iterations at a WTP threshold of $100,000/QALY gained.


CONCLUSIONS
SBRT for palliation of vertebral bone metastases is not cost-effective compared to EBRT based upon the ICER analysis with the WTP of $100,000/QALY gained. However, if median survival is ≥11 months, SBRT is economically reasonable, suggesting that selective SBRT usage in patients with longer expected survival may be the most cost-effective approach.