GAITHERSBURG, Md., Dec. 7 — Growing evidence that deadly clots can form in drug-coated stents long after they are implanted does not mean that the risks of using the tiny devices to prop open the arteries in the heart outweigh the benefits, according to a panel of experts assembled Thursday to scrutinize the troubling data.
But the group quickly agreed that the conclusion applied only to patients who had been involved in clinical trials of the two drug-coated stents now on the domestic market, Taxus, from Boston Scientific, and Cypher, from Johnson & Johnson. Such patients are generally healthier and more likely to have followed instructions about taking anticlotting drugs every day than the majority of patients currently receiving the stents. They make up well under half of the nearly one million Americans receiving stents annually.
The panel, brought together by federal regulators, will spend much of Friday considering the less reliable “real world” data on clotting risks in the far more diverse array of patients who receive the drug-coated stents in everyday practice, including groups like diabetics and patients with major blockages in multiple blood vessels.
After presentations Thursday from the two companies and a handful of other researchers, panel members disagreed about how strong the evidence was that the delayed clotting risk was a serious problem compared with the risks of using older, less expensive bare metal stents. Overall death and heart attack rates for the clinical trial patients were so low and so similar for the two groups after four years that the experts said much bigger and longer trials would be needed to answer the questions from the Food and Drug Administration.
“We’re all over the place, but I don’t think any of us think this is conclusive data,” said the chairman of the panel, Dr. William H. Maisel of Beth Israel Deaconess Medical Center in Boston.
The biggest concern for some panelists was whether the late clotting risk would continue for as long as patients had the drug-coated stents. What looks like no disadvantage at four years could become a major one over time in that case.
“I’ve seen nothing to date to suggest the problem goes away,” said Dr. Steven Nissen, a panel member who is head of the cardiovascular division of the Cleveland Clinic.
A number of studies suggest that the delayed clotting risk can be reduced by keeping patients on a daily diet of aspirin and the anticlotting drug Plavix. But how long patients can or should stay on such drugs is unclear. The group recommended that the labels doctors and patients receive with the devices include the recommendation of several medical societies that patients take Plavix for at least a year.
Stents are implanted to keep coronary arteries open after balloons have been used to push aside plaque that is clogging them in a procedure known as angioplasty. Drug-coated stents are twice as effective as bare metal devices in preventing reblockages. They were quickly embraced when they reached the market in 2003 because they help tens of thousands of patients annually avoid repeat angioplasty or bypass surgery.
The federal agency arranged the meeting because of rising concerns about reports showing that patients receiving drug-coated stents are up to five times more likely to suffer serious clots long after their implant than patients receiving bare metal stents. About 30 percent of such patients die from the clots.
If anything, the information doctors and patients might use to decide whether to use the drug-coated stents became murkier Thursday. Boston Scientific, which had previously included clotting data from the 3,500 patients in all of its trials in its reports on the risks, focused Thursday on a smaller group of just under 2,800 patients — those who got the slow-release version of Taxus that was eventually approved for use.
That smaller group was the focus on Thursday at the request of the federal agency. While the number of late clotting events in the slow-release group was still higher than in the studies of bare metal stents, the numbers involved were no longer large enough for it to be clear that the results stemmed from a real problem rather than random events.
Nevertheless, members of the panel, particularly those involved in using the devices, said the “signals” that drug-coated stents were more prone to delayed clotting pointed to a clear enough trend to warrant a warning about the developing data.
