The Wall Street Journal has published an article by Keith Winstein that looks at the methodology of the 2006 study that Boston Scientific has submitted to the Food and Drug Administration to gain U.S. approval for the Taxus Liberté coronary stent. The study, published in the Journal of the American College of Cardiology in 2007, found that Taxus Liberté stent wasn’t inferior to the Taxus Express stent, an already approved device from the company.
From the article:
Boston Scientific, of Natick, Mass., has roughly 40% of the $5 billion a year world-wide market for coronary stents. The company’s Taxus Express is the top seller in the U.S. In considering approval of the Liberte, the FDA asked the company to show that its anticlogging performance in patients was "non-inferior" to the Taxus Express.
In 2006, the company said that it met this test. Using a standard probability measure known as the "p-value," it said that there was less than a 5% chance that its finding was wrong. In April 2007, in the Journal of the American College of Cardiology, the company’s researchers for the first time specified the p-value: 4.87%.
Scientists generally regard studies with p-values above 5% to be failures, and medical journals typically won’t publish them, because they don’t provide a high level of certainty needed to ensure that results would apply to all patients, not just those under study. Put another way, science traditionally requires 95% certainty that a study proved its premise.
But the Journal’s calculations found that the Liberte study’s p-value was about 5.1% — failing to rule out the possibility that patients getting the Liberte stent will have markedly more artery recloggings than those receiving the Express.
Although the difference seems small — 0.2 of a percentage point — it is the difference between success and failure for a product on which Boston Scientific has spent some tens of millions of dollars.
In 2006, the company said that it met this test. Using a standard probability measure known as the "p-value," it said that there was less than a 5% chance that its finding was wrong. In April 2007, in the Journal of the American College of Cardiology, the company’s researchers for the first time specified the p-value: 4.87%.Read the whole thing, while it is still available: Boston Scientific Stent Study Flawed
WSJ Health Blog: Questions Raised Over Boston Scientific Stent Data…
Study abstract: Polymer-Based, Paclitaxel-Eluting TAXUS Liberté Stent in De Novo Lesions J Am Coll Cardiol, 2007; 49:1676-1683