ABSORB Trials Pit BRS Against Second-Generation DES

LONDON, England—Two late-breaking trials presented September 1, 2015, at the European Society of Cardiology Congress featured an everolimus-eluting bioresorbable scaffold (BRS).

ABSORB Japan, simultaneously published online ahead of print in the European Heart Journal, found the new device to be comparable to a conventional everolimus-eluting stent (EES) for the treatment of patients with signs of myocardial ischemia. ABSORB STEMI TROFI II, meanwhile, found similar levels of complete arterial healing between BRS and EES. 

Building the Case in Japan

The ABSORB Japan trial was designed to support regulatory approval of the Absorb BVS (Abbot Vascular) in Japan. For the study, Takashi Kimura, MD, of Kyoto University Hospital (Kyoto, Japan) and colleagues enrolled patients with signs of ischemia and 1 or 2 de novo lesions in different epicardial vessels. Patients were randomized in a 2:1 ratio to receive Absorb BVS (n = 266) or Xience Prime/Xpedition EES (n = 134; Abbott Vascular).

The BRS proved noninferior to EES for the primary endpoint of target lesion failure (TLF; composite of cardiac death, target vessel MI, or ischemia-driven TLR) at 12 months.  Definite/probable stent/scaffold thrombosis and ischemia-driven TLR were similarly rare in both groups (table 1).

Angiographic follow-up, obtained in 96.0% of lesions at 13 months, demonstrated that in-segment late lumen loss was similar between the BRS group (0.13 ± 0.30 mm) and the EES group (0.12 ± 0.32 mm; P for noninferiority < .0001).

“These positive results lay a solid foundation for continued evaluation of long-term outcomes in patients undergoing percutaneous coronary intervention with Absorb BVS,” Dr. Kimura concluded.

Discussant Steen D. Kristensen, MD, DMSc, of Aarhus University Hospital (Aarhus, Denmark), agreed with the researchers’ main conclusions but stressed that the jury is still out regarding the rationale behind BRS. With metallic DES, “in-stent thrombosis and restenosis still occur after years,” he said. “It might be an advantage if the stent is resorbed—but we currently do not know.”

BRS in STEMI

Presenting the results of ABSORB STEMI TROFI II, Patrick W. Serruys, MD, PhD, of Imperial College (London, England), pointed out that “no head-to-head comparison has been performed to assess the early phase of the arterial healing response of [BRS vs EES in STEMI patients].”

Dr. Serruys and colleagues randomized 191 STEMI patients within 24 hours of symptom onset to receive either Absorb BVS (n = 95) or Xience Xpedition (n = 96). At 6 months, patients underwent follow-up angiography and optical frequency domain imaging (OFDI). Baseline characteristics were similar between the 2 groups, although patients given BRS had greater device diameter than those given EES (mean 3.25 vs 3.12 mm; P = .005) and more frequently received postdilatation (50.5% vs 25.5%; P < .001), although at lower maximal pressure (mean 15.8 vs 18.6 atm; P = .002).

OFDI-derived healing scores at 6 months (primary endpoint) were similar at 1.74 ± 2.39 in the BVS arm and 2.80 ± 4.44 in the EES arm (P for noninferiority < .001) with a trend suggesting better healing in the BRS group (P for superiority = .053).

Also at 6 months, quantitative coronary angiography (QCA) showed lower in-device percent diameter stenosis and late loss as well as lower in-segment late loss with EES. However, both BRS and EES resulted in similar rates of in-segment binary restenosis (table 2).

Clinical events (composite of cardiac death, target vessel MI, and clinically driven TLR) had occurred in 1.1% of BRS patients and no EES patients at 6 months (P = NS). One BRS patient had subacute definite scaffold thrombosis, which led to MI and TLR. Freedom from angina was approximately 91% in each group.

“Frequencies of malapposed and both malapposed and uncovered struts were lower in the Absorb arm,” Dr. Serruys reported, “while there was no presence of intraluminal mass in [either group].”

Stringent patient selection accounts for the fact that the observed event rate in the study is “exceedingly low,” he said. Moreover, 6-month healing score only represents an intermediate step in the healing process, which is not complete until 5 years. Dr. Serruys also stressed that the results “cannot be extrapolated to other bioresorbable devices with different materials or strut thicknesses.”

Asked during a press conference if the current generation of BRS will likely become the “gold-standard” devices of that type, Dr. Serruys replied that there are indeed “some deficiencies and things we would like to improve.” Chief among them is reduction in strut thickness, he said. But in 5 years, metallic stents will start to fall out of favor, Dr. Serruys predicted, adding, “Metal will be a minority in 2020.”

Following Dr. Serruys’s presentation, discussant Gregg W. Stone, MD, of Columbia University Medical Center (New York, NY), said, “TROFI II has demonstrated that despite Absorb being a first-generation BRS with relatively thick struts and specific technique requirements, it invokes a novel healing response, which compared to metallic DES may theoretically translate into improved clinical outcomes.”

However, a large-scale randomized trial with long-term follow-up will be required to “determine the relative safety and effectiveness of these very different devices” in the STEMI setting, he added.

Note: Gregg W. Stone, MD, a coauthor of the ABSORB Japan paper, is a faculty member of the Cardiovascular Research Foundation, which owns and operates TCTMD.

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