title: Cost-effectiveness of bisphosphonate therapies for women with postmenopausal osteoporosis: implications of improved persistence with less frequently administered oral bisphosphonates.
abstract: OBJECTIVE
  Studies have shown that weekly bisphosphonate dosing results in improved persistence compared to daily dosing among patients with postmenopausal osteoporosis, yet more than 50% of patients discontinue therapy within a year. An oral, less frequent administration bisphosphonate provides an opportunity to improve persistence, a parameter not well modeled in previous cost-effectiveness analyses of osteoporosis therapies.
  
  
  METHODS
  We developed a Markov model to estimate the effect of improved persistence on the cost-effectiveness of bisphosphonates among postmenopausal women with established osteoporosis (vertebral fracture and bone mineral density T-score <or= -2.5) and an average age of 78 years. Fracture risks, clinical efficacy, mortality, resource use, costs, and utilities were obtained from the published literature. Persistence rates were derived primarily from a published clinical trial. Approximately 50% greater persistence with a monthly versus a weekly therapy was assumed on the basis of the PERSIST study, a 6-month, randomized, head-to-head prospective study that investigated treatment persistence in postmenopausal osteoporotic women on monthly versus weekly bisphosphonate therapy. Persistence was extrapolated to a maximum of 5 years. Following discontinuation, treatment benefit declined linearly and proportionally to the duration of active treatment.
  
  
  RESULTS
  Based on model estimates, more fractures were avoided (versus no treatment) with monthly bisphosphonate (58.1 per 1000 treated women) than with weekly bisphosphonates (33.8 per 1000 treated women), resulting in lower fracture care costs per woman ($7317 and $7548, respectively). The incremental cost per quality-adjusted life-year gained was lower with a monthly bisphosphonate ($13,749) than with weekly bisphosphonates ($16,657) when compared to no treatment. The incremental cost per quality-adjusted life-year of a monthly bisphosphonate was $9476 when compared to a weekly bisphosphonate.
  
  
  CONCLUSIONS
  In postmenopausal women with established osteoporosis, improvement in persistence with a less frequently administered oral bisphosphonate therapy could augment the fracture benefit and thereby improve cost-effectiveness. Further studies are required to refine the estimates of cost-effectiveness in order to address limited availability of adherence and fracture risk data.
authors.affiliation: RTI Health Solutions, 3040 Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709, USA. searnshaw@rti.org
authors.forename: S R
authors.initials: SR
authors.lastname: Earnshaw
authors.forename: C N
authors.initials: CN
authors.lastname: Graham
authors.forename: B
authors.initials: B
authors.lastname: Ettinger
authors.forename: M M
authors.initials: MM
authors.lastname: Amonkar
authors.forename: N O
authors.initials: NO
authors.lastname: Lynch
authors.forename: H
authors.initials: H
authors.lastname: Middelhoven
mesh_terms: D000284:Administration, Oral; D015519:Bone Density; D015331:Cohort Studies; D003362:Cost-Benefit Analysis; D004164:Diphosphonates / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D050723:Fractures, Bone / Q000209:etiology; D006801:Humans; D008390:Markov Chains; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications / Q000188:drug therapy*; D017698:Postmenopause; D019057:Quality-Adjusted Life Years; D012307:Risk Factors