Impact of study design on outcome after endovascular abdominal aortic aneurysm repair. A comparison between the randomized controlled DREAM-trial and the observational EUROSTAR-registry.

BACKGROUND

Patients with abdominal aortic aneurysm (AAA) can be treated by transfemoral endovascular intervention and by conventional open surgery. Level-one evidence of the safety and efficacy of one treatment mode over the other is only provided by a randomised controlled trial (RCT). Results reported by voluntary registries are considered less valid than data from RCTs. On the other hand the outcome of a RCT may not be generalisable to the common practice because of vigorous selection of patients and institutions.

PURPOSE

The outcomes reported by the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial were compared with the results of the EURopean collaborators on Stent-graft techniques for AAA Repair (EUROSTAR) registry.

METHODS

To obtain comparable study groups with regard to risk factors equal proportions of ASA I, II and III patients as observed in the endovascular arm of the DREAMtrial were selected at random from the EUROSTAR-registry. All patients had an aneurysm of at least 50mm. Only patients, who had been enrolled into the registry from 1999, were selected to avoid the influence of first generation endografts which are not longer in use. Patient characteristics and outcomes of endovascular AAA repair (EVAR) of EUROSTAR and DREAM-trial participants were compared. Differences in early findings between study groups were assessed by Chi-Square tests for discrete variables and by Wilcoxon rank sum tests for continuous variables. Follow-up variables were analysed by Kaplan-Meier and Cox proportional hazard models.

RESULTS

Data of 177 patients of the DREAM trial with randomization to EVAR and 856 patients selected in the EUROSTAR-registry were compared. Baseline characteristics were comparable between the EUROSTAR-cohort and EVAR-arm of the DREAM-trial. The 36-month survival-rate was 87.6% for EVAR-arm in the DREAM-trial similar to the 86.8% found in this EUROSTAR-study population. The freedom of secondary procedures reached after 3 years 85.7%, and 86.9% in the DREAM and EUROSTAR-cohort, respectively.

CONCLUSION

We found comparable characteristics and outcomes between patients of comparable risk class of the EUROSTAR-registry and the EVAR-cohort of the DREAM-trial. This demonstrates the following: first, the EUROSTAR-data provide reliable information, and further comparisons of registry data with patients treated by conventional AAA surgery may be justified. Secondly, the various outcomes of the randomised DREAM trial appear generalisable, as it agrees with observations in a broad common practice derived database.