Drug-coated stents facing hard 2d look
FDA to study risks of popular devicesDec 6, 2006 | Boston Globe
A Food and Drug Administration panel tomorrow will consider one of the most urgent questions in medicine: what to do about the risk of blood clots caused by drug-coated stents, tiny medical devices implanted in the arteries of millions of people.
The topic of clots has headlined national medical conferences and filled the pages of medical journals. Now it will be discussed by 19 specialists during a two-day FDA hearing in Maryland.
Behind the clotting concerns, a second issue has emerged about drug-coated stents: A small but vocal group of doctors say the devices, which cost about $2,000 apiece, may be only marginally more effective than the cheaper bare-metal stents they replaced.
Some doctors and public-health experts have begun to see the tiny mesh tubes not just as an example of a profitable fusion of drug and medical device, but as a lesson in how doctors can be seduced by an appealing new idea backed by powerful salesmanship.
Cynthia Yock, a healthcare researcher at Stanford University who has analyzed the research on drug-coated stents, calls their popularity "a fantastic case study of the companies being able to expand the market in advance of the true clinical need."
Since their arrival in 2003, drug-coated stents have become the fastest-selling medical device ever. Doctors' confidence in their benefits helped Natick stent maker Boston Scientific Corp. generate more than $2 billion annually from stent sales, growing the company into one of the world's medical-device giants.
But as evidence mounts that drug-coated stents cause dangerous blood clots in a small number of patients, cardiology leaders are taking a hard look at the benefits that led them to choose them over the older generation of bare-metal stents.
Stents hold coronary arteries open after they have been cleared of a blockage. In the clinical trial that won approval for the first drug-coated stent, Johnson & Johnson showed that 21 percent of patients who got older bare-metal stents required a repeat procedure because their arteries had re narrowed. Drug-eluting stents brought that number down to 5 percent. Boston Scientific's approval trial showed a similar drop, from 15 percent in bare-metal stents to 4 percent in drug-eluting stents.
Some newer studies show older stents may not perform as badly as suggested by those earlier trials.
An analysis published in August of more than 17,000 patients treated at 17 hospitals in the United States found just 8 percent of patients who received bare-metal stents needed to return for an artery-clearing procedure.
"In current real-life practice, bare-metal stents aren't performing as poorly as we thought they performed, and it's a bit sobering to see that," said Deepak Bhatt, a cardiologist at the Cleveland Clinic who was not involved in the analysis.
A Boston Scientific spokesman said the benefits of its Taxus stent "have been maintained in real-world use," and the company plans to back its claims by giving the FDA panel data from a global registry of 7,000 stent patients.
Dr. Sanjay Kaul, a cardiologist at Cedars-Sinai Medical Center in Los Angeles, has emerged as a critic of the widespread use of drug-eluting stents. He said the original approval trials ultimately created an exaggerated picture of the risks of bare-metal stents. The models used for comparison in the trials weren't state-of-the art, Kaul said. More importantly, he said, all patients in the trials received a mandatory angiogram, a diagnostic procedure to measure blood flow. Doctors are more likely to re intervene after seeing some artery narrowing in an angiogram, even if the patient has no symptoms.
"It's a classic example of how you stack the deck in favor of your therapy in clinical trials," Kaul said.
The FDA panel will review numerous studies of stents and listen to presentations by doctors and stent manufacturers. Its chief goal is to determine how likely drug-eluting stents are to cause long-term blood clots, and what should be done. Bhatt last week published a study saying drug-coated stents are likely to trigger a blockage in about one in 200 patients five times the rate of clotting in bare-metal stents.
A paper released online yesterday by the Journal of the American Medical Association suggests patients can reduce their risk of clotting by staying on the blood-thinning drug Plavix, but blood-thinners have complications, including a higher risk of bleeding.
The FDA is also looking at whether drug-coated stents solve a major health problem. Studies consistently show patients are less likely to have re narrowed arteries with a drug-coated stent. But many doctors are questioning whether that is worth the risk of clotting, since re narrowed arteries rarely lead to serious problems such as heart attacks.
"You have a trade-off," said Robert Califf, a Duke University cardiologist, who was the lead author of yesterday's JAMA article. "You have a less frequent, more severe risk, and a more frequent, less important benefit."
For some cardiologists, the debate has triggered a re examination of why drug-coated stents were adopted before long-term safety data became available.
Fueled by high-profile early studies and a strong sales and advertising push by manufacturers, the stents quickly captured the market.
Within two years of introduction they were used in 90 percent of procedures, even though they were technically approved only for patients with relatively simple coronary artery problems.
"If I were to teach a course in marketing," said Kaul, "I certainly would use this as an example."