TCT: Absorbable Polymer Holds Its Own for Stent Healing

WASHINGTON -- A bioresorbable polymer-based stent didn't block in-stent atherosclerotic plaque buildup better than a standard durable polymer-based drug-eluting stent, but it wasn't any worse either, the TRANSFORM-OCT trial showed.

Quantitative high-resolution imaging with optical coherence tomography (OCT) showed noninferiority for difference between the two polymer types for maximum uncovered stent length at 3 months after implantation and no significant difference by any specific measure of that endothelialization.

The co-primary endpoint of in-stent neoatherosclerosis showed noninferiority of the Synergy stent at 18 months, when its bioresorbable everolimus-eluting polymer coating should have been totally absorbed, against the Resolute Integrity stent with durable polymer-eluting zotarolimus (11.6% versus 15.9%, P=0.59). A rigorous frame-by-frame analysis of OCT imaging showed a low 1.1% of frames with neoatherosclerosis compared with 2.5% rate for the conventional stent.

The trial had been powered for superiority, but that was not met, Giulio Guagliumi, MD, of Ospedale Giovanni XXIII, in Bergamo, Italy, and colleagues reported here at the Transcatheter Cardiovascular Therapeutics (TCT )annual meeting.

One of the mechanisms of late stent failure is development of atherosclerosis in the neointimal tissue, and durable polymers have been implicated in delayed healing that may impact it.

However, "at this point there is no evidence of any additional benefit of this polymer, but what is important is the level of healing at 18 months was impressively good with the current generation of stents," Guagliumi concluded. "It doesn't matter if the polymer is bioabsorbable or durable when it's biocompatible."

Rather than dampen enthusiasm for bioabsorbable polymer, "it just confirms that it compares extremely well," Jonathan Hill, MD, of King's College Hospital in London, commented as a discussant at a TCT press conference. "We've certainly moved on from the bio-unfriendly polymers."

The real message, looking at the final outcome, was "how you get there probably doesn't matter," agreed William Gray, MD, of Lankenau Heart Institute in Wynnewood, Pa.

"The problem is when the comparator is doing so well, how can you do better?" Ori Ben-Yehuda, MD, executive director of the Cardiovascular Research Foundation (CRF) Clinical Trials Center in New York City, commented in an interview with MedPage Today. But there is a possibility that the temporary polymer will have advantages longer term, he suggested, "and I do think we need to see in higher-risk patients. We know that the process of atherosclerosis is worse in patients who have more risk factors."

Guagliumi noted that the study, which randomized 90 patients with multivessel disease to the two stents, did not involve OCT guidance for implantation, just for assessing response at 3 months and 18 months, then going forward annually out to 5 years.

The 18-month endpoint for neoatherosclerosis seemed "relatively early in the lifetime of a stent," Hill noted. But research has shown a plateau in neoatherosclerosis around 18 months, Guagliumi responded.

But after the disappointing findings with the bioabsorbable scaffold stent in ABSORB II at 3 years at the meeting, "we have to be careful about jumping to conclusions about bioresorbable, not only polymers, but also scaffolds that disappear completely," Ben-Yehuda said.

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