The use of dual-antiplatelet therapy for a period longer than 12 months in patients who had received drug-eluting stents (DES) was not significantly more effective than aspirin monotherapy in reducing the rate of MI or death from cardiac causes, based on data from two trials published in the April 15 issue of the New England Journal of Medicine.
In two concurrent clinical trials (REAL-LATE and ZEST-LATE), Seung-Jung Park, MD, from the department of cardiology at the University of Ulsan, College of Medicine and the cardiac center at Asan Medical Center in Seoul, South Korea, and colleagues randomly assigned 2,701 patients who had received DES and been free of major adverse cardiac or cerebrovascular events and major bleeding for a period of at least 12 months to receive clopidogrel (Plavix, Bristol Myers Squibb/Sanofi Aventis) plus aspirin or aspirin alone.
The primary endpoint was a composite of MI or death from cardiac causes, during a median follow-up of 19.2 months.
The cumulative risk of the primary outcome at two years was 1.8 percent with dual-antiplatelet therapy, compared with 1.2 percent with aspirin monotherapy, the researchers reported. The individual risks of MI, stroke, stent thrombosis, need for repeat revascularization, major bleeding and death from any cause did not differ significantly between the two groups.
However, Park and colleagues noted that in the dual-antiplatelet therapy group compared with the aspirin alone group, there was a non-significant increase in the composite risk of MI, stroke or death from any cause and in the composite risk of MI, stroke or death from cardiac causes. They wrote that this non-significant increase was “not anticipated,” and advised that these findings “should be interpreted with caution and the interpretation must be speculative.”
In fact, the researchers went on to say that the “results seem most likely to be due to chance, although a similar unexpected result was seen in the lower risk subgroup of patients in the…CHARISMA trial.”
The authors noted that their findings had “insufficient statistical power” and should be confirmed or refuted through larger, randomized clinical trials with longer-term follow-up.
Likewise, in the accompanying NEJM commentary, Peter B. Berger, MD, from the Geisinger Clinic in Danville, Pa., wrote that while Park et al “should be congratulated for studying this issue,” their findings cannot inform physicians’ practice because it is “an interim analysis of two ongoing, underpowered studies."
Berger concluded, “Fortunately, additional studies addressing the use of dual-antiplatelet therapy after implantation of DES are ongoing. Until then, physicians’ (and patients’) preferences and responses to uncertainty are driving practice more than the data are.”