The cost utility of bisphosphonate treatment in established osteoporosis

Hip fracture is an important and costly problem. Bisphosphonate therapy prevents hip and other fractures among women with established osteoporosis, but there are few published economic evaluations of this treatment.

To assess the cost-effectiveness of risedronate, a recently launched bisphosphonate for the prevention of fractures among women with established osteoporosis.

A state transition Markov model of established post-menopausal osteoporosis based upon randomized clinical trial data was developed. Uncertainty underlying model parameters and outcomes was dealt with using traditional sensitivity analysis and stochastic sensitivity analysis to produce quasi-95%CIs. We focussed on patients aged approximately 75 years, since this population most closely matches the randomized controlled trial, and is typical of osteoporosis patients in the UK.

The baseline model of treating a cohort of 1000 75-year-old women for 3 years with risedronate and then modelling the costs and benefits over their expected lifetimes, produced net savings of pound sterling 786 000 for the treatment group per 1000 treated women, (95%CI pound sterling 1.55m savings to pound sterling 47000 extra costs). Restricting the horizon of the analysis to only three years led to a small net cost of pound sterling 138 000 per 1000 treated women (95%CI pound sterling 196 000 savings to pound sterling 477 000 extra costs) with a net increment in Quality Adjusted Life years (QALYs) of 16 per 1000 treated women. This resulted in a cost per QALY of pound sterling 8625 per treated woman.

In this example, the use of risedronate therapy in 75-year-old women at high risk of hip fracture leads to an improvement in quality of life with possible cost savings. Restricting the analysis to a time horizon of only three years leads to a QALY gain at a modest net cost.