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An economic evaluation of strontium ranelate in the treatment of osteoporosis in a Swedish setting: based on the results of the SOTI and TROPOS trials |
Borgstrom F, Jonsson B, Strom O, Kanis J A |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The study examined the use of strontium ranelate to reduce the risk of osteoporotic fractures. Strontium ranelate consists of two atoms of stable strontium and ranelic acid. The comparator treatment was to provide no treatment.
Economic study type Cost -effectiveness analysis and cost-utility analysis.
Study population The target population comprised Swedish postmenopausal women at risk of osteoporotic fracture. In the two cohorts evaluated, the women had to be at least 50 years old with at least one radiographically confirmed vertebral fracture and a lumbar spine bone mineral density (BMD) lower than 0.840 g/cm2 (SOTI study), or at least 70 years old with a femoral neck BMD below 0.600 g/cm2 (TROPOS study).
Setting Information on the practice setting was not reported although, given the nature of the treatment, it is likely to have been primary care. The economic study was carried out in Sweden.
Dates to which data relate The dates to which the effectiveness and resource evidence referred were not given in this paper. The price year was 2004.
Source of effectiveness data The clinical data included an effectiveness measure, the incidence of new vertebral fractures and the incidence of new non-vertebral fractures over 3 years. Adverse event data such as nausea and diarrhoea were estimated from the clinical data, but were not included in the model. The epidemiological data included risk of fractures, mortality rates, risk of mortality from fractures and the relationship between bone density and fractures.
Modelling A Markov cohort model with a lifetime horizon was developed. Unlike other published models in the area, in addition to the "classical" hip, vertebral and wrist fracture types, the authors incorporated an additional health state representing other osteoporotic fracture types, thus making the model more comprehensive. The cycle length in the model was 1 year. The patients were followed through the model from the age of treatment initiation.
Sources searched to identify primary studies The effective evidence was derived from two large multi-centre randomised controlled trials (RCTs), namely, the Spinal Osteoporosis Therapeutic Intervention (SOTI) study for those women aged at least 50 and the Treatment Of Peripheral Osteoporosis Study (TROPOS) for those women above 70 years, (Meunier et al. 2004 and Reginnster et al. 2005, see 'Other Publications of Related Interest' below for bibliographic details).
The epidemiological data on fracture risks (hips, vertebrae and wrist) were taken from several studies of Swedish women. The incidence of other osteoporotic fractures was imputed from US data. The mortality rates were taken from official Swedish statistics.
Methods used to judge relevance and validity, and for extracting data The methods used to identify the data were not reported. No inclusion criteria were specified for any parameters and the selection of estimates was neither reported, nor discussed.
Measure of benefits used in the economic analysis The measures of benefits used were the quality-adjusted life-years (QALYs) and life-years (LYs) gained. The QALYs were calculated using a study based on patients recruited at the orthopaedic department at the Malmo University hospital (Zethraeus et al. 2002, see 'Other Publications of Related Interest' below for bibliographic details). A discount rate of 3% was used.
Direct costs The direct costs included those of the hospital, nursing home and health service. They covered the costs of inpatient stay, drugs, BMD measurement and physician visit. The resource use data was based on the authors' opinion, with the results of several published studies taken into consideration. The unit costs were estimated from a variety of published sources. Discounting was carried out at a rate of 3%. The price year was 2004. The study reported the average costs. The unit cost of strontium ranelate, a physician visit and a BMD measurement were given. Other unit costs were not provided. The costs of calcium and vitamin D supplements were not included as they were common to both treatment and control groups. All costs were inflated using the Consumer Price Index from Statistics Sweden.
Statistical analysis of costs The costs were given as point estimates.
Indirect Costs Productivity costs for the year following the fracture were included as they were implicitly assumed to be important. The authors also measured consumption less production as a cost. The data on productivity costs came from published studies. The costs and the quantities were not analysed separately. The price year was 2004.
Sensitivity analysis One-way sensitivity analyses were carried out on the following variables:
the risk of fractures due to a pre-existing vertebral fracture,
the mortality risk following a hip or a vertebral fracture,
the marginal cost of a clinical vertebral fracture at the end of the first year after the fracture,
the marginal cost of a physician visit and BMD measurement with strontium ranelate therapy, and
the quality of life loss after a vertebral fracture.
In addition, a second-order Monte Carol simulation was conducted to ascertain parameter uncertainty. Only effects parameters were assigned distributions.
Estimated benefits used in the economic analysis In the base-case scenario for patients with similar characteristics to those in the SOTI study, strontium ranelate resulted in 9.39 QALYS and 12.49 LYs while no treatment resulted in 9.34 QALYs and 12.45 LYs. This corresponded to an incremental benefit of 0.046 QALYs and 0.032 LYs.
In the base-case scenario for patients with similar characteristics to those in the TROPOS study, strontium ranelate resulted in 6.38 QALYs and 8.73 LYs while no treatment resulted in 6.34 QALYs and 8.71 LYs. This corresponded to an incremental benefit of 0.037 QALYs and 0.019 LYs.
The side effects of treatment were considered to be negligible.
Cost results For patients with similar characteristics to those in the SOTI study, the total intervention cost per patient was SEK 2,502,163 for the strontium ranelate group and SEK 2,480,238 for the no treatment group. This corresponded to an incremental cost of SEK 21,925.
For patients with similar characteristics to those in the TROPOS study, the total intervention cost per patient was SEK 2,168,490 for the strontium ranelate group and SEK 2,159,000 for the no treatment group. This corresponded to an incremental cost of SEK 9,490.
The costs of adverse effects were considered too small to be of relevance.
Synthesis of costs and benefits In the base-case scenario for patients with similar characteristics to those in the SOTI study, the discounted cost per QALY gained was SEK 266,549 for the strontium ranelate group and SEK 265,526 for the no treatment group. This corresponded to an incremental cost-effectiveness ratio of SEK 472,586.
In the base-case scenario for patients with similar characteristics to those in the TOPOS study, the discounted cost per QALY gained was SEK 340,099 for the strontium ranelate group and SEK 340,472 for the no treatment group. This corresponded to an incremental cost-effectiveness ratio of SEK 259,643.
Cost-effectiveness acceptability curves were produced from the Monte Carlo simulation. These showed that, if there were a willingness-to-pay of SEK 600,000 per QALY then, with the SOTI type patients, there was an 87% chance that the cost per QALY would be below this amount. With the TROPOS type patients the chance was 91%.
Other sensitivity analysis results showed that an assumption of a fracture risk reduction effect of strontium for all kinds of osteoporotic fractures reduced the cost per QALY to SEK 285,013 for SOTI type patients and to SEK 241,533 for TROPOS type patients.
The biggest increase in cost per QALY in the sensitivity analyses was caused by assuming that a vertebral fracture only reduced quality of life in the year following a fracture. This resulted in a cost per QALY of SEK 824,881 for SOTI type patients and SEK 389,172 for TROPOS type patients. The second biggest increase in cost per QALY was caused by reducing the offset time (the time after treatment discontinuation for which an effect can be detected) to zero. This caused the cost per QALY to increase to SEK 690,305 amongst SOTI type patients and to SEK 482,625 for TROPOS type patients. Increasing the offset time to 5 years resulted in a cost per QALY of SEK 419,825 for SOTI type patients and SEK 199,642 for TROPOS type patients.
Authors' conclusions The cost of giving strontium ranelate to postmenopausal women at risk of osteoporotic fracture was reasonable compared with the health benefit it produces.
CRD COMMENTARY - Selection of comparators The authors chose no treatment as a comparator for the intervention drug. This enabled the value of the new treatment, strontium ranelate, to be evaluated.
Validity of estimate of measure of effectiveness The parameters were derived from published research. The authors clearly described the different sources of the parameters. They justified their selection but did not provide any search method or inclusion criteria. The authors used large, double-blind, placebo-controlled trials as a source of clinical evidence, which was appropriate. Details of the methods used to identify the parameters would have enhanced the validity of the data used. Validity of estimate of measure of benefit The authors used two summary measures of health benefit (i.e. LYs gained and QALYs gained). The measures were derived appropriately using a Markov model. The utilities were taken from published literature, although no details of the valuation method were given.
Validity of estimate of costs The authors reported that the study had been undertaken from a societal perspective. They used the difference between production and consumption for post-retirement women to enable the calculation of future non-medical consumption, and included it as a cost. Whilst this methodology is not commonplace, some researchers deem that it reflects better the true future costs of any intervention (Meltzer 1997, see 'Other Publications of Related Interest' below for bibliographic details). The paper did not detail all the costs included, therefore it was unclear whether all relevant costs had been considered. The resource quantities and unit costs were taken from published sources. The costs were converted to year 2004 and discounted at a rate of 3%.
Other issues The authors compared their findings with other work on osteoporosis, although not with work that had identical aims. The issue of generalisability was addressed, and the authors were clear that they were interested in the results for Sweden and that the results could not necessarily be generalised to other countries. The authors do not appear to have presented their results selectively and their conclusions reflected the scope of their analysis.
The authors acknowledged several limitations of their analysis. First, the assumption of a 100% compliance rate might have led to an overestimation of the costs. Second, the impact on fracture risk of pre-existing non-vertebral fractures was not taken into account because of the lack of reliable measures; however this would have led to an underestimation of fracture risk. Finally, the risk of fracture could have been underestimated due to the fact that the model only accounted for one fracture per year, although the effect of this is likely to have been very small.
Implications of the study Within the caveats outlined, the authors suggested that strontium ranelate is likely to be cost-effective in comparison with no treatment. They made no suggestions for further research.
Source of funding Funded by a grant from Servier.
Bibliographic details Borgstrom F, Jonsson B, Strom O, Kanis J A. An economic evaluation of strontium ranelate in the treatment of osteoporosis in a Swedish setting: based on the results of the SOTI and TROPOS trials. Osteoporosis International 2006; 17(12): 1781-1793 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Meunier PJ, Roux C, Seeman E, et al. The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. N Engl J Med 2004;350:459-68.
Reginster JY Seeman E, De Vernejoul MC, et al. Strontium ranelate reduces the risk of nonvertebral fractures in postmenopausal women with osteoporosis: Treatment of Peripheral Osteoporosis (TROPOS) study. J Clin Endocrinol Metab 2005;90:2816-22.
Meltzer D. Accounting for future costs in medical cost-effectiveness analysis. J Health Econ 1997;16:33-64.
Zethraeus N, Borgstrom F, Johnell O. Costs and quality of Life associated with osteoporosis related fractures - results from a Swedish survey. Working Paper Series in Economics and Finance. Stockholm: School of Economics; 2002. Report No.: 512.
Indexing Status Subject indexing assigned by NLM MeSH Aged; Aged, 80 and over; Bone Density Conservation Agents /economics /therapeutic use; Clinical Trials, Phase III as Topic; Cost-Benefit Analysis /economics; Female; Fractures, Bone /epidemiology /etiology; Health Care Costs; Humans; Markov Chains; Organometallic Compounds /economics /therapeutic use; Osteoporosis, Postmenopausal /drug therapy /economics /epidemiology; Quality of Life; Quality-Adjusted Life Years; Risk Factors; Sweden /epidemiology; Thiophenes /economics /therapeutic use; Treatment Outcome AccessionNumber 22006002204 Date bibliographic record published 31/07/2007 Date abstract record published 31/07/2007 |
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