Cost Effectiveness of Denosumab versus Oral Bisphosphonates for Postmenopausal Osteoporosis in the US

Abstract

In the US, 26 % of women aged ≥65 years, and over 50 % of women aged ≥85 years are affected with postmenopausal osteoporosis (PMO). Each year, the total direct health care costs are estimated to be $US12-18 billion. The cost effectiveness of denosumab versus oral bisphosphonates in postmenopausal osteoporotic women from a US third-party payer perspective was evaluated. A lifetime cohort Markov model was developed with seven health states: 'well', hip fracture, vertebral fracture, 'other' osteoporotic fracture, post-hip fracture, post-vertebral fracture, and dead. During each cycle, patients could have a fracture, remain healthy, remain in a post-fracture state or die. Relative fracture risk reductions, background fracture risks, mortality rates, treatment-specific persistence rate, utilities, and medical and drug costs were derived using published sources. Expected costs and quality-adjusted life years (QALYs) were estimated for generic alendronate, denosumab, branded risedronate, and branded ibandronate in the overall PMO population and high-risk subgroups: (a) ≥2 of the following risks: >70 years of age, bone mineral density (BMD) T score less than or equal to -3.0, and prevalent vertebral fracture; and (b) ≥75 years of age. Costs and QALYs were discounted at 3 % annually, and all costs were inflated to 2012 US dollars. Sensitivity analyses were conducted by varying parameters e.g., efficacies of interventions, costs, utilities, and the medication persistence ratio. In the overall PMO population, total lifetime costs for alendronate, denosumab, risedronate, and ibandronate were $US64,400, $US67,400, $US67,600 and $US69,200, respectively. Total QALYs were 8.2804, 8.3155, 8.2735 and 8.2691, respectively. The incremental cost-effectiveness ratio (ICER) for denosumab versus generic alendronate was $US85,100/QALY. Risedronate and ibandronate were dominated by denosumab. In the high-risk subgroup (a), total costs for alendronate, denosumab, risedronate and ibandronate were $US70,400, $US70,800, $US74,000 and $US76,900, respectively. Total QALYs were 7.2006, 7.2497, 7.1969 and 7.1841, respectively. Denosumab had an ICER of $US7,900/QALY versus generic alendronate and dominated all other strategies. Denosumab dominated all strategies in women aged ≥75 years. Base-case results between denosumab and generic alendronate were most sensitive to the relative risk of hip fracture for both drugs and the cost of denosumab. In each PMO population examined, denosumab represented good value for money compared with branded bisphosphonates. Furthermore, denosumab was either cost effective or dominant compared with generic alendronate in the high-risk subgroups.