ABSORB III: Everolimus Eluting Bioresorbable Scaffolds for Coronary Artery Disease

Original Title: Everolimus-Eluting Bioresorbable Scaffolds for Coronary Artery Disease. Reference: Stone, M.D. for the ABSORB III Investigators. N Engl J Med 2015;373:1905-1915.

The ABSORB III is part of a series of randomized studies that test bioresorbable scaffolds in the clinical practice (ABSORB II, EVERBIO II, ABSORB Japan, and ABSORB IV). 2008 patients were randomized; 60% had stable angina, 25% unstable angina and 10% silent ischemia. Treatment was assigned 2:1 for the everolimus eluting bioresorbable scaffold “Absorb” (BVS) (Abbott Vascular, n= 1332) and the cobalt chromium “Xience” (Abbott Vascular, n=686) (DES). Patients with acute myocardial infarction and complex lesions were excluded. The study was described as ‘non-inferiority’, estimating 2000 patients would be necessary to achieve a 96% predictive power, assuming a 7% rate of target vessel treatment failure with both devices.

Primary end point was a combination of cardiac death, target lesion infarction and ischemia driven target lesion revascularization of at one year, even though clinical follow up would be at five years.

Primary end point occurred in 7.8% of the Absorb group patients, compared to 6.1% of Xience patients (difference 1.7 percentage points; confidence interval 95%, 0.5 to 3.9; p=0.007 for non-inferiority and P=0.16 for superiority). There were no significant differences in cardiac death (0.6% and 0.1%, respectively; p=0.29), target vessel infarction (6.0% and 4.6%, respectively; P=0.18) or ischemia driven revascularization (3.0% and 2.5%, respectively; P=0.50).
Stent thrombosis occurred in 1.5% of patients in the Absorb group and in 0.7% of patients in the Xience group (p=0.13).

In this group of patients with non-complex coronary lesions, the everolimus eluting bioresorbable scaffold “Absorb” is not inferior to the cobalt chromium eluting Xience in the composite of death, infarction or target lesion revascularization at one year.

Editorial Comment
Events such as thrombosis distant from stent, an accelerated neoatherosclerosis, or permanent vessel mobility disruption, are decisive elements to assume a better evolution away from bioresorbable scaffolds over bare metal stents. The ABsrob III is the largest of the randomized compared studies published so far, where authors conclude that bioresorbable scaffolds are not inferior to bare metal stents in the above mentioned combination of events at one year follow up. However, a few considerations must be taken into account: 4.4% of patients assigned to bioresorbable vascular scaffolds (BVS) were treated with DES; thrombosis rate in the BVS group was 1.5% which, even though not statistically different to the 0.7% in the Xience group, seems an exaggeration for the present standard of such low risk population; only 65% of the BVS group and 51% of the DES group received post dilation; finally, the statistical analysis was of the intention to treat cohort, based on non-inferiority criteria, which could underestimate the differences, as expressed in a Byrne editorial (N Engl J Med 373;20:1969-70); in fact, the absolute difference of 1.7% increases to 2% (8% vs 6%) when examining the populations receiving the assigned treatments.

Courtesy of Dr Agustín Vecchia.
Hospital Alemán, Buenos Aires, Argentina.