Decision analysis model evaluating the cost of a temporary hydrogel rectal spacer before prostate radiation therapy to reduce the incidence of rectal complications

Purpose: We conducted a decision analysis to evaluate the cost effectiveness of a newly Food and Drug Administration approved rectal spacer gel (SpaceOAR, Augmenix) for the reduction of rectal toxicity of prostate radiation therapy (RT). Methods: A decision tree model (TreeAge Pro) was used to compare the strategy of pretherapy placement of a spacing hydrogel before RT to RT alone. The model compared costs associated with rectal complications because of rectal toxicity over a 10-year period across 3 different RT modalities. Rectal toxicity rates were estimated from studies on conformal RT dose escalation, high-dose stereotactic body radiotherapy (SBRT) and low-dose SBRT. Rectal toxicity reduction rates (baseline reduction 70%) were estimated from recently published 15 month data using a rectal spacer. Direct and indirect cost estimates for established grades of rectal toxicity were based on national and institutional costs. Reduction in short-term complications were assumed to carry forward to a reduction in long-term toxicity. One-way and two-way sensitivity analyses were performed. Results: The overall standard management cost for conformal RT was $3,428 vs. $3,946 with rectal spacer for an incremental cost of $518 over 10 years. A 1-way sensitivity analyses showed the breakeven cost of spacer at $2,332 or a breakeven overall risk reduction of 86% at a cost of $2,850. For high-dose SBRT, spacer was immediately cost effective with a savings of $2,640 and breakeven risk reduction at 36%. However, 2-way spacer cost to risk reduction sensitivity analyses were performed. Conclusion: The use of a rectal spacer for conformal RT results in a marginal cost increase with a significant reduction in rectal toxicity assuming recently published 15 month rectal toxicity reduction is maintained over 10 years. For high-dose SBRT it was cost effective. Further studies would be necessary to validate the long-term benefits of rectal spacers.