While an extended analysis of the SPIRIT II study showed that after two years the Abbott Xience V stent may continue to hold a clinical edge over Boston Scientific’s Taxus, the difference is no longer statistically significant, according to a presentation at the 2008 American College of Cardiology (ACC) Scientific Sessions.
Initial results of the SPIRIT II trial, released in September 2006, showed that the Xience V stent was superior to the Taxus stent in both six-month findings on angiography and one-year clinical outcomes.
Patrick W. Serruys, MD, and colleagues from Thoraxcenter, Erasmus Medical Center in Rotterdam, The Netherlands, recruited 300 patients from 28 medical centers in Europe, New Zealand and India, who needed stenting of up to two new coronary lesions. Patients were randomly assigned to treatment with the Xience V everolimus-eluting stent or the Taxus paclitaxel-eluting stent.
The study primarily intended to document in-stent late loss at six months. The initial SPIRIT II results were significantly better for the Xience V stent when compared to the Taxus stent. At one-year follow-up, the combined rates of major adverse cardiac events (MACE), consisting of cardiac death, heart attack and repeat procedure to treat the target lesion, were also significantly better in the Xience V group, according to the researchers.
New data from a late-stage evaluation showed that, although the Xience V stent continued to show a trend toward improved clinical outcomes compared to the Taxus stent at two years, the differences between the two stents were no longer statistically significant.
The investigators found that the overall MACE rate at two years was 40 percent lower in patients treated with the Xience V stent (6.6 percent vs. 11.0 percent in the Taxus group). Repeat procedures to treat the target lesion were performed in 3.8 percent and 6.8 percent of patients, respectively, a 44 percent reduction favoring the Xience V stent.
Similarly, the researchers said that the rates of heart attack were 2.8 percent and 5.5 percent, respectively, a 49 percent reduction, and the rates of cardiac death were 0.5 percent and 1.4 percent, respectively, a 64 percent reduction. There was no difference in the rates of blood clotting inside the stent or stent thrombosis at two years.
In 117 patients who had follow-up angiography at two years, the researchers said that there was no significant difference in the rates of re-narrowing of at least 50 percent (binary restenosis) within the stents (2.1 percent with the Xience V stent vs. 2.9 percent with the Taxus stent). In-stent late loss was virtually identical (0.33 mm vs. 0.34 mm, on average, respectively), Serruys reported.
In his commentary, David Cohen, director of research at the Mid-America Heart Institute and Saint Luke’s Hospital in Kansas City, Mo., called the SPIRIT II trial “an eloquent study,” and despite the study’s sponsor, the endpoint was not to affirm the superiority of Xience V over Taxus. He also commented on the “excellent” two-year follow-up record of the researchers with a loss of only 1.6 percent of the patient population.
Cohen noted that the most interesting aspect between the six-month and two-year outcomes was the way the gap closed between the two stents. The lack of late-stage events with Xience V, however, is a statistical anomaly, he said. As a result, he questioned whether the late angiographic “catch-up” would continue or if there eventually would be increased late target lesion revascularization events.
However, Cohen concluded that SPIRIT II was a high-quality study that adds important news to the industry’s understanding of the long-term outcomes of the Xience V.
Abbott Vascular, maker of Xience V, funded the study.