Cost-effectiveness of zoledronic acid (ZOL) versus denosumab (Dmab) in prevention of skeletal-related events (SREs) in metastatic breast cancer (mBC).

Abstract

9025 Background: Dmab has been approved in the United States for prevention of SREs in mBC on the basis of the results of a phase III trial comparing Dmab vs. ZOL in mBC. In this trial, overall survival, disease progression, and serious adverse events (SAEs) were similar across treatments. The cost of a Dmab injection ($1,650) is nearly 2x that of ZOL’s ($887). This analysis assessed the cost effectiveness of Dmab vs. ZOL in mBC from a U.S. managed care perspective. Methods:A literature-based Markov model was developed to estimate the survival, quality-adjusted life-years (QALYs), number and costs of SREs, and drug and administration (Dmab=$32.46; ZOL=$153.86) costs for patients (pts) receiving Dmab or ZOL. Inputs were selected to reproduce the phase III trial outcomes up to 28 months. QALYs were estimated by assigning utilities to health states (prior to SRE; SRE; post-SRE, and death). SRE-related costs and utilities were obtained from the literature. Per-event SRE costs ranged from $4,039 (vertebral fracture) to $20,734 (bone surgery). In sensitivity analysis, SAEs were included ($15,441/pt with a SAE). Future outcomes were discounted at 3%/year. Results: Dmab resulted in fewer SREs, more QALYs, and lower SRE-related costs, but higher drug-related and total costs vs. ZOL, resulting in an incremental cost of $6,884/pt (Table). The cost per QALY gained was $644,000 when excluding SAEs ($613,000/QALY when including SAEs). Conclusions: Dmab is predicted to result in an incremental cost/QALY gained >$600,000. This high cost/QALY is due to the higher drug acquisition cost of Dmab, combined with the limited prevention of SREs and lack of overall survival/disease progression benefits vs. ZOL. The cost/QALY of Dmab is far higher than what is considered to be good value for a medical intervention ($50,000 to $100,000/QALY), thus raising questions regarding Dmab’s value in mBC. ZOL Dmab Difference Cumulative SREs/pt 1.010 0.694 -0.317 Total discounted QALYs/pt 0.9405 0.9512 +0.0107 Discounted costs Drug, administration, monitoring $15,994 $25,016 +$9,023 SREs $7,290 $5,152 -$2,138 Total $21,284 $30,168 +$6,884 Cost/QALY gained $643,726 Costs in 2010 U.S. dollars.