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WASHINGTON -- Thinner struts and biodegradable polymers haven't made metallic drug-eluting stents (DES) work significantly better for patients at high bleeding risk, according to a subanalysis of the BIO-RESORT trial.

One-year target vessel failure rates came out no different when these percutaneous coronary intervention (PCI) patients got one of two biodegradable-polymer DES with very thin struts (6.5%) or a durable-polymer DES with a slightly larger 91-μm bare strut thickness (7.3%, HR 0.88, 95% CI 0.54-1.46).

Individual components of the primary endpoint also numerically favored the biodegradable polymer group without reaching statistical significance, reported Clemens von Birgelen, MD, PhD, of Thoraxcentrum Twente in the Netherlands, at the meeting here:

• Cardiac death: 1.8% versus 2.1% (HR 0.85, 95% CI 0.33-2.15)
• Target vessel MI: 2.7% versus 3.3% (HR 0.81, 95% CI 0.38-1.72)
• Target vessel revascularization: 2.3% versus 3.0% (HR 0.74, 95% CI 0.33-1.64)

"At 1-year follow-up of these patients, very thin-strut biodegradable polymer DES showed a similar safety and efficacy as a thin-strut durable polymer DES," concluded von Birgelen. "This is an explorative analysis of the BIO-RESORT randomized trial at 1-year, and the findings should be considered hypothesis generating."

Trading out a durable polymer for a biodegradable one has been thought to reduce vessel wall inflammation and delayed vessel healing. No clinical benefits of biodegradable over durable DES have been demonstrated as of yet, even if overall event rates have been relatively low.

"That the biodegradable polymer has no clear advantage over the durable polymer in this analysis is not surprising or disappointing to me, though we still have to see if any favorable differences emerge with longer durations of follow up." said Deepak Bhatt, MD, of Brigham and Women's Hospital and Harvard Medical School in Boston, who was not a part of the trial.

The good news is that there are now a number of excellent DES options that are evidence-based, according to Bhatt, and this might make DES prices come down in the U.S. "The study also provides further indirect evidence that DES are the preferred stent even in high bleeding risk patients, so I don't really see any role for bare metal stents anymore," he said.

Also in question is the future of bioresorbable vascular scaffolds and biodegradable-polymer DES, suggested Eric Bates, MD, of University of Michigan in Ann Arbor, in commenting on the study. "The biggest advance in stent technology appears to have been in producing thinner struts which have been associated with clinical benefit and make the currently available stents hard to improve upon," he said.

BIO-RESORT investigators randomized PCI patients to the Synergy biodegradable everolimus-eluting stent (n=1,172), Resolute Integrity durable zotarolimus-eluting stent (n=1,173), or the Orsiro biodegradable sirolimus-eluting stent (n=1,169).

Main findings from the non-inferiority trial showed that the Synergy and Orsiro DES were on par with the Resolute Integrity in the all-comer population at 1 year.

The present substudy included the 28.7% considered to be at high bleeding risk, predominantly due to older age and being on oral anticoagulation. One caveat to the study was that the BIO-RESORT criteria for high bleeding risk were slightly different from those in other trials.

Follow-up data was available at 1 year for 98.8% of patients, von Birgelen's group reported. Compared with the majority of trial participants with lower bleeding risk, high bleeding risk patients were less likely to be on dual antiplatelet therapy after PCI and more likely to be on the combination of an oral anticoagulant and P2Y12 inhibitor instead.

Stent thrombosis rates reached 0.5% and 0.6% of the biodegradable and durable DES groups, respectively, at 1 year (HR 1.34, 95% CI 0.22-8.02).

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