TCT: ISAR-TEST fails to prove superiority of Xience over Cypher, but trends up

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WASHINGTON, D.C.--The Xience V everolimus-eluting stent and Cypher sirolimus-eluting stents provide comparable clinical outcomes out to two years, based on results of ISAR-TEST 4 trial presented as a late-breaking clinical trial Sept. 24 at the annual Transcatheter Cardiovascular Therapeutics (TCT) conference.

Because the original trial was designed to assess biodegradable polymer drug-eluting stents (DES) with permanent polymer DES, ISAR TEST is not powered to assess differences between the two stents in a head-to-head fashion, explained lead author Robert A. Byrne, MD, from Medizinische Klinik, Klinikum rechts der Isar, Technische Universität in Munich, Germany, who presented the trial.

For the original randomized, two-center trial, the researchers included 2,603 patients with de novo lesions, and randomized them to either a biodegradable polymer DES (1,299 to BP-DES) or a permanent polymer DES (1,304 to Xience or Cypher), which was published in the European Heart Journal. They included patients with de novo coronary artery stenosis of at least 50 percent and symptoms or objective evidence of ischemia, and excluded patients with left main disease or cardiogenic shock.

For the current focus, there were 1,304 patients in the original permanent polymer DES arm; the Xience arm (652 patients) had 94 percent clinical follow-up at two years, and the Cypher arm (652 patients) had a clinical follow-up rate of 95 percent at two years.

At two years, the Cypher arm had a rate of 18.8 percent for the primary endpoint of cardiac death, target vessel MI and target lesion revascularization rate, and 16 percent in the Xience arm—which is not a statistically significant difference between the platforms.

For the secondary endpoint of definite and probable stent thrombosis, the rate in the Cypher arm was 1.9 percent and 1.4 in the Xience arm. This also does not represent a statistically significant difference.

When assessing definite stent thrombosis, the researchers discovered a difference of 0.6 in the Xience arm—with two cases of early stent thrombosis, two cases of late stent thrombosis and no cases of very late stent thrombosis. Cypher had a definite stent thrombosis of 1.4, with three cases of early stent thrombosis, five cases of late stent thrombosis and one case of very late stent thrombosis.

Byrne reported that the efficacy endpoint assessing target lesion revascularization was 13.5 percent in the Cypher arm and 9.9 percent in the Xience stent.

“While there was a trend towards superior anti-restenotic efficacy with Xience, specifically-powered studies are needed to evaluate the clinical significance of this finding,” Byrne concluded.

In his commentary of the trial, David J. Cohen, MD, director of cardiovascular research at St. Luke’s Mid America Heart Institute in Kansas City, Mo., said that this is one of the first "reasonably sized" comparisons of the first-generation Cypher to the second-generation Xience. "While questions about the first-generation Taxus paclitaxel-eluting stent [Boston Scientific] have been more definitively answered through large trials, there is less definitive information on Cypher, but data are consistently reinforcing the strength of the Xience platform,” he concluded.