Stent-Supported Percutaneous Angioplasty of the Carotid Artery versus Endarterectomy (SPACE) study
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The Stent-Supported Percutaneous Angioplasty of the Carotid Artery versus Endarterectomy (SPACE) study was a randomised non-inferiority trial of 1200 patients with symptomatic carotid-artery stenosis >=50% by NASCET criteria. In the trial 605 patients underwent Carotid-artery stenting (CAS) and 595 underwent Carotid Endarterectomy (CEA) Carotid-artery stenting (n=605) vs Carotid endarterectomy (n=595).
30-day ipsilateral ischaemic stroke or death 6·84% carotid-artery stenting 6·34% carotid endarterectomy Absolute difference 0·51% (90% CI –1·89%-2·91%) 4 events in 30 days (41 vs 37)
The non-inferiority margin SPACE failed to prove non-inferiority of carotid-artery stenting compared with carotid endarterectomy for the periprocedural complication rate. The results of this trial do not justify the widespread use in the short-term of carotid-artery stenting for treatment of carotid-artery stenoses. Results at 6–24 months are awaited.
Trial was stopped early after only 1200 patients despite an original enrollment target of 1900 patients. Assuming a primary endpoint event rate of 5% in both treatment groups 1900 patients would achieve a power of 80% to show that the true event-rate difference is <2.5%. However, an interim analysis after 1200 patients showed with the current observed event rates and difference in complications between the two arms would only achieve a 50% power to detect the event-rate difference between the two groups. Further, the trial wouldrequire another 2500 patients to achieve 80% power. Given this difference the trial sponsors withdrew support.
Due to the early termination of the study the observed absolute difference of .50 between the groups allowed the 90% CI to cross 0 (1.89% to 2.91%).
Therefore, SPACE did not enroll enough patients (underpowered) to demonstrate non-inferiority and it is hard to draw conclusions from the study.
Embolic Protection Use
Despite evidence supporting EPD use decreases event rates, EPD use was only 27% in the CAS group.
Exclusion of Operators
Questions about the generalizability of the findings remain due to limited operator experience at many of the included centers and exclusion of 10 originally planned centers.