News:CoStar Drug Eluting Stent is not Non-inferior to TAXUS Drug Eluting Stents

April 23, 2008 by Rene Franco M.D.

The CoStar stent is a new cobalt chromium alloy drug eluting stent (DES) designed to release paclitaxel without the use of a durable surface polymer coating. Its bioresorbable poly-lactic-co-glycolic acid polymer allows complete polymer bioresorption after drug delivery, only the biologically inactive bare-metal platform remains afterwards. It is thought that among other factors, durable polymer surface coatings in first generation DES may play a role in the occurrence of the infrequent but catastrophic late stent thrombosis.

In the last issue of the Journal of the American College of Cardiology, the primary results of the COSTAR (Cobalt Chromium Stent With Antiproliferative for Restenosis) II trial were published. This multicenter, prospective, single-blind, randomized clinical trial conducted by Krucoff et al was designed to compare the 8-month clinical outcomes of patients with both single and multivessel coronary stenoses undergoing elective percutaneous coronary intervention (PCI) with either the CoStar or the Taxus DES.

A total of 1,700 patients from 71 sites in the U.S., Germany, Belgium and New Zealand undergoing elective PCI were enrolled. Patients were randomly assigned 3:2 to Costar or Taxus. Randomization was stratified by single or multivessel status. The primary end point was 8 month major adverse cardiac events (MACE) defined as a hierarchical composite of cardiac or unknown death, Q-wave and non-Q-wave MI and clinically driven target vessel revascularization (TVR).

At hospital discharge MACE was 2.6% with CoStar ( 0% death, 2.4% MI and 0.2% clinically driven TVR) and 1.6% with TAXUS (0% death, 1.6% MI and 0% TVR) p=0.16. The rate of MACE at 30 days was 3.4% with CoStar ( 0% death, 2.8% MI, 1.0% clinically driven TVR) and 1.9% with TAXUS (0% death, 1.6% MI and 0.2% clinically driven TVR) p= 0.063.

At 8 month follow-up the rate of MACE with CoStar was 11%(0.5% death, 3.4% MI and 8.1% clinically driven TVR) and 6.9% with TAXUS (0.7% death, 2.4% MI and 4.3 clinically driven TVR) p= 0.005. The significantly lower rate of MACE with Taxus compared to CoStar was found to be predominantly due to the significantly lower incidence of clinically driven TVR in the former group (8.1% and 4.3% respectively. p= 0.002). The incidence of late stent thrombosis was 0.1% with the use of both DES and therefore statistically non significant.

In patients with single-vessel stenoses, CoStar patients had a higher incidence of 8-month MACE than patients receiving TAXUS (9.9% and 6.1% respectively, p= 0.015). Patients with multivessel involvement had a similar trend but statistical significance was not reached because of the small number of patients in the multivessel cohort (15.4% and 9.7% respectively. p= 0.125).

The 9-month angiographic follow-up of 456 lesions in 286 patients showed that per vessel in-segment late loss, diameter stenosis and binary angiographic restenosis(BAR) were all significantly better in the Taxus group compared to the CoStar group (p<0.0001, p<0.0001 and p=0.0002 respectively). Regarding the in-stent late loss, diameter stenosis and BAR all were significantly better with TAXUS stent (p<0.0001 for the 3 end points).

The results from this multicenter, randomized study showed significant differences between the TAXUS DES and the CoStar DES in angiographic as well as clinical outcomes.

Conclusion cannot be reached that CoStar DES is non-inferior to TAXUS DES.