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PARIS -- Among patients who undergo revascularization using stents, prolonging dual antiplatelet therapy beyond six months may not be beneficial, the randomized PRODIGY trial showed.

Among those receiving a bare-metal stent or one of three drug-eluting stents, the rate of all-cause death, MI, or stroke was not significantly different (P=0.91) in patients treated with an antiplatelet agent such as clopidogrel (Plavix) plus aspirin for six months compared with those who continued dual antiplatelet therapy for 24 months -- 10% versus 10.1% -- according to Marco Valgimigli, MD, PhD, of the University of Ferrara in Italy.

A shorter duration of clopidogrel use was, however, associated with a decrease in II, III, or V BARC bleeding (3.5% versus 7.4%; HR 0.46, P=0.00018), he reported at the European Society of Cardiology meeting here.

Valgimigli said that even though the study could not rule out a reduction in the risk of cardiovascular events of less than 40%, the risk of bleeding, in a relative sense, is greater than any potential benefit based on this study.

"Current recommendations may have overemphasized the benefit over the risk of prolonging aspirin and clopidogrel," he said at a press briefing.

Additionally, the study did not provide information about individual patient characteristics, including lesion length and comorbidities.

Guidelines from the American College of Cardiology/American Heart Association call for at least 12 months of dual antiplatelet therapy after stenting, and those from the ESC call for six to 12 months. Both documents are based on registry data, resulting in uncertainty, Valgimigli said.

Of note, the ACC/AHA developed the current guidelines following concern about the risk of late stent thrombosis, a risk initially reported at the ESC meeting in 2006.

By the end of 2006, the FDA had convened a special two-day hearing to evaluate the safety of drug-eluting stents, and stent-makers and academics issued a new definition of stent thrombosis.

Magnus Ohman, MD, a cardiologist from Duke University, said the findings of the current study -- which involved about 2,000 patients -- do not call the ACC/AHA guidelines into question, even though the findings are consistent with two other studies.

Ohman, a member of the ACC/AHA Task Force on Practice Guidelines who was not involved in the study, said he is awaiting the results of the Dual Antiplatelet Therapy (DAPT) trial, which is ongoing in the U.S. and involves about 20,000 patients.

"The question is still out and I wouldn't change the guidelines based on this small trial," he said.

The PRODIGY trial was conducted at three centers in Italy. The researchers initially randomized patients with either stable coronary artery disease or acute coronary syndromes in whom stenting was planned to receive either a third-generation bare-metal stent or one of three drug-eluting stents -- zotarolimus-eluting (Endeavor), paclitaxel-eluting (Taxus), or everolimus-eluting (Xience).

After 30 days, patients in each stent group were then randomized to either a short duration of dual antiplatelet therapy with clopidogrel (six months in most patients) or a longer duration of 24 months; 1,970 patients were randomized. All patients received aspirin for the full two years.

From 31 days after stent implantation to two years, there was no significant difference based on the duration of clopidogrel in the rate of all-cause death, MI, or stroke (HR 0.98, 95% CI 0.74 to 1.29). There was also no difference in rates of the individual components of the endpoint or in stent thrombosis.

Even when the analysis was restricted to six months through two years -- when only one group was receiving clopidogrel -- there was no difference in the rate of cardiovascular events.

An analysis broken down by stent type has not yet been completed, Valgimigli said.

But even though there was no difference in adverse cardiovascular events, 24 months of clopidogrel was associated with more bleeding by all definitions and a greater need for transfusion (P<0.05 for all).

David Holmes, MD, president of the ACC, said that the findings of one study are not enough to overturn guidelines, but said the current study is an important piece of information to consider because there is still uncertainty regarding the optimal duration of dual antiplatelet therapy.

The decision about whether to continue clopidogrel beyond 12 months is best left to the patient and physician, said Holmes, who is a cardiologist at the Mayo Clinic in Rochester, Minn.

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