Endovascular stents for abdominal aortic aneurysms: a systematic review and economic model.
OBJECTIVE
To determine the clinical effectiveness and cost-effectiveness of endovascular aneurysm repair (EVAR) of infrarenal abdominal aortic aneurysms (AAAs) in patients at varying levels of risk.


METHODS
The following bibliographic databases were searched (2005-February 2007): BIOSIS Previews, CINAHL, Cochrane Central Register of Controlled Trials, EMBASE, ISI Proceedings, MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, Science Citation Index and Zetoc Conferences.


METHODS
A systematic review of the clinical effectiveness of EVAR was performed using standard methods. Meta-analysis was employed to estimate a summary measure of treatment effect on relevant outcomes based on intention to treat analyses. A second systematic review was undertaken to identify existing cost-effectiveness analyses of EVAR compared with open surgery and non-surgical interventions. Two new decision models were developed to inform the review.


RESULTS
Six RCTs were included in the clinical effectiveness review. Thirty-four studies evaluated the role of patients' baseline characteristics in predicting risks of particular outcomes after EVAR. The majority were based on data relating to devices in current use from the EUROSTAR registry. Compared with open repair EVAR reduces operative mortality (odds ratio 0.35, 95% CI 0.19 to 0.63) and medium-term aneurysm-related mortality (hazard ratio 0.49, 95% CI 0.29 to 0.83) but offers no significant difference in all-cause mortality. EVAR is associated with increased rates of complications and reinterventions, which are not offset by any increase in health-related quality of life. EVAR trial 2 comparing EVAR with non-surgical management in patients unfit for open repair found no differences in mortality between groups; however, substantial numbers of patients randomised to non-surgical management crossed over to receive surgical repair of their aneurysm. The cost-effectiveness systematic review identified six published decision models. Both models considered relevant for the decision in the UK concluded that EVAR was not cost-effective on average compared with open repair at a threshold of 20,000 pounds per quality-adjusted life-year (QALY). Another model concluded that EVAR would be on average more cost-effective than no surgical intervention in unfit patients at this threshold. The Medtronic model concluded that EVAR was more cost-effective than open repair for fit patients at this threshold. The York economic evaluations found that EVAR is not cost-effective compared with open repair on average at a threshold of 30,000 pounds per QALY, with the results very sensitive to model assumptions and the baseline risk of operative mortality. Exploratory analysis to evaluate management options in patients unsuitable for open surgery suggested that the cost-effectiveness of EVAR may be sensitive to aneurysm size and patient's age at operation. Indicative modelling suggests that EVAR may be cost-effective for small aneurysms in some patient groups. Ongoing RCTs will provide further evidence relating to these patients.


CONCLUSIONS
Open repair is more likely to be cost-effective than EVAR on average in patients considered fit for open surgery. EVAR is likely to be more cost-effective than open repair for a subgroup of patients at higher risk of operative mortality. These results are based on extrapolation of mid-term results of clinical trials. Evidence does not currently support EVAR for the treatment of ruptured aneurysms. Further follow-up of the existing UK trials should be undertaken and the relative costs of procedures and devices should be investigated further.
Chambers
D
D
Centre for Reviews and Dissemination, University of York, UK.
Epstein
D
D
Walker
S
S
Fayter
D
D
Paton
F
F
Wright
K
K
Michaels
J
J
Thomas
S
S
Sculpher
M
M
Woolacott
N
N
D017544:Aortic Aneurysm, Abdominal / Q000191:economics* / Q000401:mortality / Q000628:therapy*; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D006801:Humans; D019057:Quality-Adjusted Life Years; D016032:Randomized Controlled Trials as Topic; D015607:Stents / Q000191:economics*; D006113:United Kingdom