Absorbable stents non-inferior….but is that enough?

A coronary artery stent that scaffolds the vessel immediately after angioplasty but disappears over time has been proposed as means to avoid complications of late stent thrombosis and restore physiological vasomotion.  Bioabsorbable platforms (termed scaffolds) are designed to slowly dissolve over 2 to 3 years, leaving little or no residue in the vessel.  However, conventional stent technology sets a very high bar with low rates of late complications, many years of operator experience, and large numbers of prior trials.  In the ABSORB III trial a total of 2008 patients with stable or unstable angina were randomized in a 2:1 fashion to revascularization with either the ABSORB bioabsorbable scaffold or a conventional drug-eluting stent (in this case the everolimus-eluting XIENCE platform).  The study was designed as a non-inferiority trial with a primary end-point of cardiac death, target-vessel myocardial infarction, or ischemia-driven target-lesion revascularization.  At 1 year of follow-up, the study demonstrated no significant difference in the primary end-point (7.8% vs. 6.1%, P=0.007 for noninferiority and P=0.16 for superiority) and no significant difference between the two groups in the individual components of the end-point.  However, it the point-estimates for adverse events were higher among patients receiving the bioabsorbable scaffold.

Conclusions

In this large study comparing first generation bioabsorbable coronary scaffolds against conventional third generation metallic drug-eluting stents, the bioabsorbable scaffolds demonstrated non-inferiority within the pre-specified margin of 4.5% in terms of both efficacy and safety.  However, the point estimates for bioabsorbable scaffolds in this trial raise concern about the true benefits, and even potential for harm, of this new technology.  Longer term data in larger studies is needed prior to wholesale adoption of absorbable coronary scaffolds in clinical practice.

Summarized by Hussain Contractor and Steven M. Bradley

Ellis SG, Kereiakes DJ, Metzger DC, Caputo RP, Rizik DG, Teirstein PS, Litt MR, Kini A, Kabour A, Marx SO, Popma JJ, McGreevy R, Zhang Z, Simonton C, Stone GW; ABSORB III Investigators. Everolimus-Eluting Bioresorbable Scaffolds for Coronary Artery Disease. N Engl J Med. 2015 Oct 12. [Epub ahead of print]

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