COST-EFFECTIVE TREATMENT THRESHOLDS FOR OSTEOPENIC POSTMENOPAUSAL WOMEN IN JAPAN

Purpose: Treatment guideline in Japan recommends medical treatment for osteopenic postmenopausal women who have no previous clinical fractures but with at least one additional fracture risk factor such as current smoking, high intake alcohol or family history of fractures. However, its cost-effectiveness has not been adequately assessed. The purpose of this study is to estimate the cost-effectiveness of alendronate treatment for osteopenic postmenopausal women in Japan considering bone mineral density (BMD) and other BMD-independent risk factors.

Method: The cost-effectiveness analysis was conducted from the perspective of Japan healthcare system. Markov model with six health states (no fracture, post-vertebral fracture, post-hip fracture, post-vertebral and hip fracture, bedridden, and death) was developed to predict lifetime costs and effects (QALYs: quality-adjusted life years) associated with ten years of alendronate therapy and no drug treatment in postmenopausal women aged 65 years without fracture history. Risk functions for age and femoral neck BMD-specific fractures were constructed by using data from epidemiologic studies in Japan. Mortality rates, direct medical costs, utility values, and relative risk of drug therapy for fractures were estimated from other published sources. For the base-case analysis, we ran the model with deferent femoral neck T-score (-2.4, -2.0 and -1.5) and risk factor, using 1st order Monte Carlo simulations with 1,000 trials each. In addition, probabilistic sensitivity analysis was performed to assess parameter uncertainty.

Result: Incremental cost-effectiveness ratio (ICER) of treating Japanese postmenopausal women who have one additional fracture risk factor with T-score of -2.4, -2.0 and -1.5 ranged from $31,898 to $32,548, $53,903 to $59,335 and $103,212 to $113,108 per QALY gained, respectively. For women with T-score of -1.5 and two additional risk factors, ICER ranged from $60,845 to $66,686 per QALY gained. For women with three risk factors, ICER was estimated at $36,133 per QALY gained. Then the probabilities of being cost-effective were estimated in the range of 98.5 to 99.1%, applying the willingness to pay thresholds of $63,500~$67,000 (6.35~6.70 million JPY; 1$ = 100JPY, Ohkusa et al., 2006) per QALY gained.

Conclusion:   Medical treatment for Japanese postmenopausal women with femoral neck T-scores less than -2.0 would be cost-effective. Also our study suggests that multiple risk factors should be considered in treating osteopenic postmenopausal women who have relatively high BMD in terms of cost-effectiveness.