Trials Take on Permanent- vs. Biodegradable-Polymer Technology

PARIS, France—Two trials at EuroPCR 2012 used optical coherence tomography (OCT) to document similarly good vessel healing between next-generation biodegradable-polymer stents and a second-generation drug-eluting stent (DES) equipped with a permanent polymer. The data were presented on Wednesday, May 16.

STACCATO Lends Support to Permanent-Polymer DES

For the STACCATO (Stent sTrut Apposition and Coverage in Coronary ArTeries) trial, Tom Adriaenssens, MD, of University Hospital Leuven (Leuven, Belgium), and colleagues randomized 64 ACS patients—21 STEMI, 21 NSTEMI, and 22 stable/unstable angina—with de novo lesions in a 1:1 ratio to receive Xience V/Promus everolimus-eluting stents (EES; Abbott Vascular; Boston Scientific) or Biomatrix biolimus A-9-eluting stents (BES; Biosensors, Singapore). Baseline patient and procedural characteristics were similar between the 2 groups. Approximately 20% of lesions were occluded and nearly half were located in the LAD.

OCT analysis showed similar prevalence of malapposed struts between EES and BES immediately after implantation, but by 9 months, EES had fewer uncovered struts (primary endpoint) and higher mean neointimal thickness. Uncovered struts were consistently less common in EES than in BES patients regardless of clinical presentation, though the differences were not significant (table 1).

Table 1. STACCATO: OCT Results

The percentage of uncovered struts was highest in NSTEMI patients (8.5%), followed by stable/unstable angina (6.9%) and STEMI patients (4.6%; P = 0.08).

Session co-chair Javier Escaned, MD, PhD, of Hospital Clinico San Carlos (Madrid, Spain), asked how differences in the platforms might have affected results. Biomatrix stents have a strut thickness of 130 μm and are made of stainless steel whereas Xience V/Promus stents measure 89 μm and consist of cobalt chromium.

“It's hard to say. Maybe there's an effect of the drug, or an effect of the polymer,” Dr. Adriaenssens replied, adding that post-dilatation could also create cracks in the stent that might influence healing. “Another explanation could be that at 9 months we just were too early in our assessment. Maybe if we repeated the analysis at 2 years, the biolimus-eluting stent would catch up in its healing” as the polymer is reabsorbed.

ISAR-TEST-6 OCT Builds the Case for Equivalence

In the ISAR-TEST-6 OCT trial, Julinda Mehilli, MD, of Deutsches Herzzentrum (Munich, Germany), and colleagues compared 2 'limus-eluting' stents that had either biodegradable- or permanent-polymer coatings. The researchers included patients (n = 34) with stable/unstable angina or a positive stress test and de novo lesions (n = 41) in native coronary arteries. Patients were randomized to receive the Nobori BES (Terumo, Tokyo, Japan), which has a biodegradable polymer, or Xience V EES.

At 6- to 8-month follow-up, OCT imaging was obtained in 14 BES patients (n = 17 lesions, n = 2,805 struts) and in 19 EES patients (n = 22 lesions, n = 3,890 struts). Lack of coverage and malapposition again were both numerically more common with BES, while median neointimal thickness was higher with EES, but the disparities did not reach statistical significance (table 2).

Table 2. ISAR-TEST-6-OCT: Strut-Level Analysis  

However, the proportion of lesions with at least 30% uncovered stent struts was numerically lower with BES than with EES, at 17.7% vs. 23.8%, respectively (P = 0.78).

Overall, “[t]hese data suggest a comparable safety and efficacy profile of these 2 new-generation DES in patients with de novo lesions out to 6- to 8-month follow-up,” Dr. Mehilli concluded.

Sources:

1. Adriaenssens T. STACCATO - Stent sTrut Apposition and Coverage in Coronary ArTeries: An OCT study. Presented at: EuroPCR. May 16, 2012. Paris, France.
2. Mehilli J. Randomised comparison of limus-eluting stents with biodegradable polymer or permanent polymer coatings regarding stent coverage assessed by OCT. Presented at: EuroPCR. May 16, 2012. Paris, France.

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