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Note: On Nov. 6, 2018, it was reported that the SORT OUT IX investigators made a statistical error, such that they erroneously concluded that the study demonstrated noninferiority. A full explanation appears here.

SAN DIEGO -- Challengers to the Orsiro stent met their non-inferiority goals and forced the question: are thinner struts really better in drug-eluting stent technology?

First up was the zotarolimus-eluting Resolute Onyx, which was associated with a 4.5% rate of target vessel failure at 1 year among all-comers patients in the BIONYX trial. This was statistically similar with the 4.7% rate of Orsiro (P=0.0005 for non-inferiority).

Both devices performed similarly in the individual endpoint components of combined cardiac death, target vessel-related MI, and clinically-driven target vessel revascularization, reported Clemens von Birgelen, MD, PhD, of Thoraxcentrum Twente in Amsterdam, in a late-breaking trial presentation at the Transcatheter Cardiovascular Therapeutics (TCT) conference.

What was striking, however, was that just 0.1% of Resolute Onyx recipients experienced stent thrombosis over the study period versus 0.7% of those who got Orsiro (HR 0.11, 95% CI 0.01-0.87), though von Birgelen cautioned that this was a hypothesis-generating finding.

Even with the difference in stent thrombosis, there are no clear advantages for one stent over the other, his group said. "The frequencies of the individual components of the primary endpoint were similar and quite low in both groups, which could be perceived as a positive signal of safety for both devices," he noted.

The were simultaneously published in the Lancet. Part of the reason the journal decided to take the BIONYX results was because of the "ridiculously low" stent thrombosis rate that "made us stop and think whether this was an indication that we reached the end of the comparisons of stents this way," said Stuart Spencer, the journal's executive editor.

"How much further do we have to go to go below 0.1% in stent thrombosis?" he asked.

Nevertheless, chance probably played a big role in that "really amazing" figure, cautioned Manel Sabaté, MD, of University Hospital Clinic in Barcelona. He advocated longer-term follow-up of the Resolute Onyx.

This stent improves on the visibility of its predecessor, the Resolute Integrity, by having a thin composite wire strut with a dense platinum-iridium core.

Struts measure 81 µm or 91 µm thick uncoated, making the Resolute Onyx slightly thicker than the Orsiro (60 µm or 80 µm). Another difference between the two is that the former elutes zotarolimus over 6 months, the latter sirolimus over 3.3 months.

BIONYX was conducted at seven centers in Belgium, Israel, and the Netherlands. Randomized were all-comers patients requiring percutaneous coronary intervention (n=2,488) who were age 64 on average. Also, 23.9% were women and 95.3% were white. Over half presented with an acute MI.

Baseline characteristics were largely similar between groups, as was the prescribing of dual antiplatelet therapy (DAPT) at hospital discharge and 1 year.

"Orsiro was chosen as the reference stent, because it has shown excellent safety and efficacy outcomes in three all-comer trials. In addition, most recently Orsiro outperformed the former best-in-class everolimus-eluting stent in the most-comer patients of the BIOFLOW V trial," von Birgelen noted.

His group acknowledged that lower-than-expected event rates may have taken away from the statistical power of their analyses.

In another TCT presentation, the Biolimus A9-coated BioFreedom stent also proved itself to be Orsiro's equal in 1-year data from SORT OUT IX.

Patients randomized to the polymer-free BioFreedom stent in this non-inferiority trial had target lesion failure occur in 5.3% over the first year versus 4.0% of Orsiro group (P=0.01 for non-inferiority), according to Lisette Jensen, MD, DMSc, PhD, of Odense University Hospital in Denmark. By then, stent thrombosis reached 0.7% in both groups (RR 1.00, 95% CI 0.43-2.30).

Target lesion revascularization was more likely with the BioFreedom (3.5% vs 1.3%, RR 2.77, 95% CI 1.66-4.62). However, this device appears to be at a disadvantage in efficacy, Jensen suggested.

Like BIONYX, SORT OUT IX was performed in an all-comers population (n=3,151), this time patients getting PCI at four Danish centers who had follow-up data collected from registries. DAPT lasted 6 months in stable angina patients and 12 months in the case of acute coronary syndrome.

BioFreedom is markedly thicker than the Orsiro given its 120-µm struts.

The dogma for stents has been that the smaller the struts the better, said TCT session discussant Sigmund Silber, MD, PhD, who is in private practice in Munich, Germany, adding that he was no longer convinced.

What SORT OUT IX does is it provides reassuring data about the safety profile of the BioFreedom, commented panelist Giulio Stefanini, MD, PhD, of Humanitas University Pieve Emanuele-Milan. "We had concern after LEADERS FREE, but we can safely state today the events then were due to the higher risk of the population, not the device."

"I completely agree with the remark that it's assuring from the safety point of view," said panelist Philip Urban, MD, of Hôpital de la Tour in Meyrin, Switzerland.

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