BIONYX trial demonstrates noninferiority of durable zotarolimus-eluting stent to bioresorbable sirolimus-eluting stent
Percutaneous coronary intervention (PCI) with a thin composite wire strut, durable polymer-coated stent demonstrated comparable results to that using an ultrathin cobalt-chromium strut, bioresorbable polymer-coated stent, according to results of the BIONYX* trial presented at the recent TCT symposium (TCT 2018).
“Treatment with both stents was similarly safe and effective with excellent 1-year clinical outcomes in a complex all-comer patient population,” said study lead author Professor Clemens von Birgelen from the Thoraxcentrum Twente, Enschede, the Netherlands.
Participants in this multicentre (seven sites in Belgium, Israel, and the Netherlands), noninferiority trial were 2,488 patients (mean age 64 years, 23.9 percent female) who were randomized to undergo PCI with either a thin composite wire strut, zotarolimus-eluting durable polymer-coated stent (n=1,243) or an ultrathin cobalt-chromium strut, sirolimus-eluting bioresorbable polymer-coated stent (n=1,245). About 71 percent of patients presented with acute coronary syndrome, 29.1 percent with stable angina or silent ischaemia, and 51.2 percent with acute myocardial infarction (MI).
At 1 year, target vessel failure – a composite of cardiac death, target-vessel-related MI, and clinically indicated target vessel revascularization – was comparable between patients who received the durable and bioresorbable stents (4.5 percent vs 4.7 percent, absolute risk difference, -0.2 percent, 95 percent confidence interval [CI], -1.9 to 1.4 with upper limit of one-sided 95 percent CI exceeding 1.1 percent establishing noninferiority of the durable stent to the bioresorbable one; p=0.0005). [Lancet 2018;doi:10.1016/S0140-6736(18)32001-4]
Incidence of cardiac death was low and comparable between patients who received the durable and bioresorbable stents (0.6 percent vs 1.1 percent, hazard ratio [HR], 0.54; p=0.18), as was target-vessel-related MI (1.5 percent in each group), and target vessel revascularization (3.2 percent vs 3.1 percent, HR, 1.02; p=0.92).
Stent thrombosis (probable or definite) occurred more frequently among patients who received the bioresorbable stent compared with the durable one (n=9 vs 1, HR, 0.11, 95 percent CI, 0.01–0.87; p=0.0112).
“The vast majority of contemporary stents use stent platforms from cobalt-chromium alloy which allows for the creation of fine mesh tubes with satisfactory radial force, but limited x-ray visibility,” said von Birgelen. “Suboptimal radiographic visibility can be challenging in obese patients, when treating bifurcated or calcified coronary lesions, or when carefully assessing stent expansion,” he said, explaining the purpose for the development of the durable zotarolimus-eluting stent.
“The metallic stent platform consists of a composite wire made from a dense platinum-iridium core, which makes the struts radiopaque, and an outer layer of cobalt-chromium alloy. The dense core also allows for reduced strut thickness, which might be associated with a decreased risk of stent thrombosis,” said von Birgelen and co-authors.
“Despite the difference in stent strut materials and thicknesses and the dissimilar durable and bioresorbable polymer coatings of the two study stents, the BIONYX study found no advantage for one stent over the other,” said von Birgelen, recommending further research into the low incidence of stent thrombosis in patients using the durable stent.
The authors highlighted the importance of follow-up data which will reveal the long-term outcomes and stent thrombosis rates after cessation of dual antiplatelet therapy, and acknowledged that results may differ in cardiac centres with fewer “experienced operators”.
However, Drs Edoardo Camenzind and Batric Popovic from the Université de Lorraine in France advised caution when interpreting the findings of a noninferiority trial. “[N]oninferiority trials are sensitive to many methodological issues that potentially affect the final results and are not powered to provide definitive information about safety, particularly when they are powered for a combined safety-efficacy endpoint. The stent thrombosis data from [this] study … warrant further investigation to identify possible causes, although the between-group differences are most likely due to chance,” they said in a commentary. [Lancet 2018;doi:10.1016/S0140-6736(18)32334-1]