1. THE EFFECTIVENESS OF ANNUAL ZOLEDRONIC ACID INFUSION VERSUS ORAL BISPHOSPHONATE: A MODELLING APPROACH
Terence Ong1, 2, Matthey Jones3, Opinder Sahota1
1Department of Healthcare for Older People, Queens Medical Centre, Nottingham, United Kingdom
2Division of Rehabilitation and Ageing, University of Nottingham, United Kingdom
3Division of Primary Care, university of Nottingham, United Kingdom
Introduction
Results
Persistence with oral bisphosphonates is poor.1 Low persistence is associated with increased risk of fractures and hospitalisation.2 An annual bisphosphonate infusion, zoledronic acid could address this problem.
Of the 45,995 women in Nottingham City ≥50years, it was estimated that 15,332 have osteoporosis. Over three years, there would be an estimated 460 VF and 460 HF. If all women received ZA (assuming a 90% compliance), there would be 69% less VF (141 cases) and 37% less HF (290 cases). When these figures were compared with both a 70% and 50% oral bisphosphonate compliance, there would be 236 and 260 more VF cases; 19 and 62 more HF cases respectively.
This would represent a total healthcare cost for treating VF/HF over three years in Nottingham City
Objectives
As no direct comparison of zoledronic acid (ZA) and oral bisphosphonate (alendronic acid, AA; risedronic acid, RA) have been evaluated in a clinical trial, this study aims to compare the clinical and cost-offset of an annual ZA infusion with oral bisphosphonate, AA and RA, in fracture reduction using a predictive model.
Methods
The model compared patients prescribed either ZA or oral bisphosphonate (ratio AA:RA, 5:1 based on UK prescribing data1).
The model was applied to 1/3 of Nottingham city’s population of women ≥50 years (Office of National Statistics) estimated to have osteoporosis4
Compliance percentages were predetermined and set based on clinical relevance for a three-year treatment period (90% for ZA; 70% and 50% for oral bisphosphonates).
Three year reduction in relative risk (RR) of hip fractures (HF) and vertebral fractures (VF) were calculated from pivotal randomised clinical trials (ZA-Black 2007;3 AA-Black 1996,5 Cummings 19986; RA-Reginster 2000,7 McClung 20018). Patients not compliant with treatment were considered to have a fracture risk similar to the placebo arm of the trials (rate calculated by pooling together data from the trials’ placebo arm).
Treatment costs over three years (hospital and outpatient) were derived from Stevenson 2006 (£1706 for each VF; £10,760 for each HF).9
Fig. Decision tree analysis based on risk of fracture depending on persistence or non-persistence with either zoledronic acid, alendronic acid, risedronic acid or no treatment
of £3.97million at a 70% oral bisphosphonate compliance; and £4.47million at a 50% oral bisphosphonate compliance. This is a 15.3% to 24.8% increase in healthcare expenditure.
Conclusion
Poor compliance with oral bisphosphonate is associated with increased fracture numbers and healthcare cost. Current data suggests this may be as low as 30% at 3 years. An annual ZA infusion, which is now available in a generic preparation, can address this problem.
References
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Black D., et al. Randomised trial of effect of alendronate on risk of fracture in women with existing vertebral fractures. Lancet. 1996:348:
Cummings S., et al. Effect of alendronate on risk of fracture in women with low bone density but without vertebral fractures. JAMA. 1998:280:
Reginster J.Y., et al. Randomised trial of the effects of risedronate on vertebral fractures in women with established postmenopausal osteoporosis. Osteoporos Int. 2000:11:83-91
McClung M., et al. Effect of risedronate on the risk of hip fracture in elderly women. N Engl J Med. 2001:344:
Stevenson M. D., et al. The hospitalisation costs and out-patient costs of fragility fractures. Women’s Health Medicine. 3:4