Absorb Stent With Bioabsorbable Scaffold Comparable to Everolimus-Eluting Stent

September 08, 2015

LONDON, UK — Data from two new studies presented last week at the European Society of Cardiology (ESC) 2015 Congress provide some evidence the everolimus-eluting stent with a bioabsorbable vascular scaffold (Absorb, Abbot Vascular) is as good as the current standard of care[1].

For patients who received the Absorb stent, the primary end point of target lesion failure at 12 months was 4.2% compared with 3.8% among patients who received the everolimus-eluting stent with a nonabsorbable cobalt-chromium scaffold (Xience, Abbott Vascular), a difference that was not statistically significant. The study, which was designed as a noninferiority trial, met its primary end point, report investigators.

Regarding the secondary end point, which was an angiographic end point measuring in-segment late lumen loss, the loss was 0.13 mm with the Absorb stent and 0.12 for the Xience stent (P=0.74).

Presenting the results of the 400-patient ABSORB Japan study during the late-breaking clinical-trials session, investigators, led by Dr Takeshi Kimura (Kyoto University Hospital, Japan) and Dr Gregg Stone (Columbia University Medical Center/New York-Presbyterian Hospital, NY), also reported data on the 12-month clinical outcomes and showed no difference in the rate of cardiac death, target vessel MI, or ischemia-driven target lesion revascularization between the two treatment groups.

The rate of stent thrombosis at 12 months was 1.5% in both stent arms. More than 93% of patients were taking dual antiplatelet therapy at 12 months.

Dr Takeshi Kimura

Kimura, who presented the results to the media, said the ABSORB trial was designed to support regulatory approval of the Absorb stent in Japan, and because of that the trial has limitations, one of the most notable being the inclusion of highly selected coronary artery disease patients typical of stent trials designed for regulatory approval. The study also had a large noninferiority margin for the primary clinical end point and an event rate lower than expected.

During the same ESC session, Dr Patrick Serruys (Imperial College London, UK) presented data from the ABSORB TROFI II study, an imaging study in 191 patients with STEMI[2]. The primary end point was a healing score at 6 months measured by intracoronary optical frequency domain imaging (OFDI), a second-generation optical coherence tomography (OCT)–derived imaging method. Like ABSORB Japan, patients were randomized to treatment with the Absorb stent or the Xience everolimus-eluting stent.

Investigators reported that "Absorb in the setting of STEMI resulted in nearly complete arterial healing, which was comparable to that of the metallic [everolimus-eluting stent] at 6 months." In addition, the frequency of malapposed, as well as malapposed and uncovered, struts were lower in the Absorb-treated patients.

Dr Patrick Serruys

During the press conference, Serruys said one aspect of the Absorb stent that could be improved would be a reduction in strut thickness. Still, he suspects metallic stents in the coronary arteries "will be a minority in 2020."

Dr Steen Kristensen (Aarhus University Hospital, Denmark), the discussant following the late-breaking clinical-trials presentation, who wrote an editorial accompanying the study's publication in European Heart Journal[3], said the new stents have the benefit of delivering the drug and then disappearing, changing a "coronary intervention from treatment with a permanent metallic stent to a resorbable cure."

Despite their potential benefit, Kristensen homed in on the rate of stent thrombosis in ABSORB Japan. At 1.5%, this is high, considering the low-risk nature of the patients, he argued. In studies with the Xience stent, the rate of stent thrombosis in an all-comer population has been reported to be as low as 0.2%, a number that is tough to beat.

"Other registries have reported a fairly high incidence of stent thrombosis in patients with bioresorbable stents," writes Kristensen. "The occurrence and clustering of stent thrombosis in the subacute phase suggests that the risk is associated with factors related to the scaffold, the lesion, implantation technique, or a combination of these factors (calcium, adequate predilatation, expansion, apposition etc)."

He acknowledges, however, that operators are "are still learning to use this device." At the present time, the bioabsorbable scaffold might offer a clinical advantage, and with that the use of metallic stents might wane in the future, but "we currently do not know," said Kristensen.

Abbott Vascular sponsored ABSORB Japan and ABSORB TROFI II. Kimura and Serruys both serve on advisory boards for Abbott Vascular. Disclosures for the coauthors are listed in the paper. Kristensen and the other editorialists report no relevant financial relationships.

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