More Clots in Bioresorbable vs Metal Stents in 1-Year, Six-Trial Study

Marlene Busko

December 11, 2015

MUNICH, GERMANY — A meta-analysis of six trials comparing 1-year outcomes in patients randomized to receive PCI with an everolimus-eluting bioresorbable vascular-scaffold stent (Absorb, Abbott Vascular) or an everolimus-eluting conventional metal stent revealed that the "disappearing" stent conferred a twofold greater risk of stent thrombosis and greater late lumen loss, although the rates of repeat revascularization were similar with both strategies[1].

The meta-analysis by Dr Salvatore Cassese (Munich University, Germany) and colleagues, published online November 16, 2015 in the Lancet, analyzed data from three trials of Absorb that were presented at TCT 2015, two trials that were presented at the ESC 2015 Congress, and one other trial.

In these six trials, 2337 patients received the Absorb stent and 1401 patients received a cobalt-chromium stent (Xience V, Xience Prime, or Xience Expedition, Abbott Vascular; n=1321) or a platinum–chromium stent (Promus Element, Boston Scientific; n=80).

Finding "at least similar efficacy vs the existing best-in-class drug-eluting stent at 12 months is important," according to Cassese and colleagues. "The primary benefit of biodegradable vs metallic stents is expected to emerge several years after index [PCIs], when the elution of antirestenotic drug is completed and the bioresorbable scaffold is dissolved," they add. Thus longer, larger trials are needed to fully assess the advantages of bioresorbable stents.

The disappearing stents "may in the long run be much better than the others, but at the moment, we must acknowledge that we have a little more to learn," Dr Renu Virmani (CVPath Institute, Gaithersburg, MD), who coauthored an accompanying editorial with Aloke V Finn, MD (Emory University, Atlanta, GA)[2], told heartwire from Medscape.

Absorb promised less thrombosis, but "that's not going to be true when you put in such thick stents," she noted. Similarly, vessels with the bioresorbable stents did not become "babylike" but instead there was more late lumen loss in this meta-analysis.

"We need 5-year data to be able to say that bioresorbable stents are better than drug-eluting stents—that patients live longer, don't come back with diseases, don't have restenosis, and don't get stent thrombosis," according to Virmani. "If that happens, then I think they are for most patients who have large vessels."

Meta-Analysis to Compare Stents' 1-Year Outcomes

The everolimus-eluting bioresorbable scaffold stent has been widely studied, but the trials comparing it with everolimus-eluting metal stents have been short and too small to assess safety and efficacy clinical end points, Cassese and colleagues write.

Thus, they performed this meta-analysis of six trials that compared these two stent types in patients with ischemic heart disease who received percutaneous revascularization: ABSORB China (480 patients), ABSORB II (501), ABSORB III (2008), ABSORB Japan (400), EVERBIO II (158), and TROFI II (191).

The primary efficacy outcome was target lesion revascularization, and the primary safety outcome was definite or probable stent thrombosis. The secondary outcomes were target lesion failure (a composite of cardiac death, target-vessel MI, or ischemia-driven target lesion revascularization), MI, death, and late lumen loss.

The patients were mainly men with a median age of 62, and about 70% of the lesions had a complex morphology.

At a median follow-up of 1 year, a similar percentage of patients in the bioresorbable-stent group (3%) and in the metal-stent group (3.3%) had target lesion revascularization.

However, significantly more patients in the bioresorbable-stent group (1.3%) than in the metal-stent group (0.5%) had definite or probable stent thrombosis. The highest risk of stent thrombosis in the bioresorbable stent group occurred within 1 to 30 days after implantation (odds ratio 3.11; 95% CI 1.24–7.82; P=0.02).

Similarly, more patients who received the bioresorbable stent had an MI during follow-up (5.2%) compared with patients who received a metal stent (3.5%), but this difference was not significant.

A total of 30 patients (1%) died, with similar numbers in both patient groups, but this outcome varied widely in the six trials.

Last, angiographic data for 1265 (96%) of the lesions at a median of 10.5 months showed that lesions treated with the bioresorbable stents had significantly greater in-device and in-segment late lumen loss.

Risk of Outcomes, Bioresorbable Vascular Scaffold Stent vs Metal Stent*

Outcome Odds Ratio (95% CI) P
Target lesion revascularization 0.97 (0.66–1.43) 0.87
Definite or probable stent thrombosis 1.99 (1.00–3.98) 0.05
Target lesion failure 1.20 (0.90–1.60) 0.21
MI 1.36 (0.98–1.89) 0.06
Death 0.95 (0.45–2.00) 0.89
In-device late lumen loss 0.08 (0.05–0.12) <0.001
In-segment late lumen loss 0.05 (0.01–0.09) 0.01
*Both stent types were everolimus-eluting

Finn and Virmani conclude that "although much progress has been made, we need to wait to see whether bioresorbable stents can fulfil their promise—in both the short term and long term."

Cassese has no relevant financial relationships; disclosures for the coauthors are listed in the article. Finn has received research grants from Medtronic and Boston Scientific and personal fees from Medtronic Vascular and is an advisory board member for Medtronic. Virmani is an advisory board member for Abbott Vascular, Medtronic, and 480 Biomedical; has received fees for speaking from Merck; honoraria or fees from Abbott Vascular, Biotronik, Boston Scientific, Medtronic, Microport Medical, OrbusNeich Medical, Terumo, Merck, 480 Biomedical, WL Gore, and Bard Lutonix; and research support from Abbott Vascular, BioSensors International, Biotronik, Boston Scientific, Medtronic, Microport Medical, OrbusNeich Medical, SINO Medical Technology, Terumo, Merck, 480 Biomedical, WL Gore, and Bard Lutonix.

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