SPACE-2: A Missed Opportunity to Compare Carotid Endarterectomy, Carotid Stenting, and Best Medical Treatment in Patients with Asymptomatic Carotid Stenoses

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Background

Because of recent advances in best medical treatment (BMT), it is currently unclear whether any additional surgical or endovascular interventions confer additional benefit, in terms of preventing late ipsilateral carotid territory ischemic stroke in asymptomatic patients with significant carotid stenoses. The aim was to compare the stroke-preventive effects of BMT alone, with that of BMT in combination with carotid endarterectomy (CEA) or carotid artery stenting (CAS) in patients with high grade asymptomatic extracranial carotid artery stenosis.

Methods

SPACE-2 was planned as a three-armed, randomized controlled trial (BMT alone vs. CEA plus BMT vs. CAS plus BMT, ISRCTN 78592017). However, because of slow patient recruitment, the three-arm study design was amended (July 2013) to become two parallel randomized studies (BMT alone vs. CEA plus BMT, and BMT alone vs. CAS plus BMT).

Results

The change in study design did not lead to any significant increase in patient recruitment, and trial recruitment ceased after recruiting 513 patients over a 5 year period (CEA vs. BMT (n = 203); CAS vs. BMT (n = 197), and BMT alone (n = 113)). The 30 day rate of death/stroke was 1.97% for patients undergoing CEA, and 2.54% for patients undergoing CAS. No strokes or deaths occurred in the first 30 days after randomization in patients randomized to BMT. There were several potential reasons for the low recruitment rates into SPACE-2, including the ability for referring doctors to refer their patients directly for CEA or CAS outwith the trial, an inability to convince patients (who had come “mentally prepared” that an intervention was necessary) to accept BMT, and other economic constraints.

Conclusions

Because of slow recruitment rates, SPACE-2 had to be stopped after randomizing only 513 patients. The German Research Foundation will provide continued funding to enable follow up of all recruited patients, and it is also planned to include these data in any future meta-analysis prepared by the Carotid Stenosis Trialists Collaboration.

Keywords

Carotid stenosis
Carotid endarterectomy
Carotid stenting
Randomized trial
Best medical treatment

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Dittmar Böckler, Department of Vascular and Endovascular Surgery, University of Heidelberg, Heidelberg, Germany; Hartmut Brückmann, Department of Neuroradiology, Ludwig-Maximilians-Universität, Munich, Germany; Eike Sebastian Debus, Department of Vascular Surgery, University Hospital of Hamburg, Hamburg, Germany; Jens Fiehler, Department of Neuroradiology, University Hospital of Hamburg, Hamburg, Germany; Gustav Fraedrich, Department of Vascular Surgery, University of Innsbruck, Innsbruck, Austria; Harald Mudra, Department of Cardiology, Pulmonology and Internal Intensive Care Medicine, Städtisches Klinikum München, Klinikum Neuperlach, Munich, Germany; Jürg Schmidli, Department of Vascular Surgery, University Hospital of Bern, Bern, Switzerland; Robert Stingele, Department of Neurology, DRK Kliniken Berlin, Berlin, Germany; Ralf Zahn, Department of Cardiology, Angiology and Internal Intensive Care Medicine, Klinikum Ludwigshafen, Ludwigshafen, Germany; Martin Böhm, Department of Internal Medicine, University Hospital of Homburg/Saar, Homburg, Germany; Erich Bernd Ringelstein, formerly Department of Neurology, University Hospital of Münster, Münster, Germany; Klaus Mathias, formerly Department of Radiology, Klinikum Dortmund, Germany.