乌鸦传媒

WASHINGTON -- The news keeps getting worse for the Absorb bioabsorbable scaffold stent.

While prior results had raised concerns about target lesion failure and stent thrombosis edging the wrong way compared with a conventional drug-eluting metallic scaffold Xience stent, 2-year results from the pivotal ABSORB III trial showed that the gap had widened to a cumulative target lesion failure rate of 11.0% versus 7.9% (hazard ratio 1.42, 95% CI 1.04-1.94, P=0.03).

After excluding the one-fifth of patients who got the device in smaller vessels than allowed, the HR was still 1.35 (95% CI 0.93-1.96, P=0.12).

Target-vessel MI rates were 7.3% versus 4.9% over 2 years (P=0.04), although not a significant difference in those with vessels of at least 2.25 mm.

Although , of the Cleveland Clinic, called the findings "generally acceptable" during a late-breaking clinical trial session at the American College of Cardiology (ACC) annual meeting, the FDA wasn't so generous.

It issued a "Dear Doctor" letter the morning of the presentation pointing to an "increased rate of major adverse cardiac events observed in patients receiving the BVS [bioabsorbable vascular scaffold], when compared to patients treated with the approved metallic XIENCE drug-eluting stent."

The agency said it will investigate and "is working with Abbott Vascular, Inc. to conduct additional analyses to better understand the cause(s)" and will continue to monitor the stent's performance in ongoing clinical studies and in adverse events reports submitted to it.

Session discussant , of Mount Sinai Hospital in New York City, expounded on the implications for practice:

"We are somewhat comforted to see that the event rates are not extremely high as others had been thinking about. However, it is important for us to focus on the fact that this is breakthrough technology, and that we are waiting for the promise of the future superiority of this device to the current best-available metallic DES; that is really what physicians, patients, and everyone is looking for. I think we're going to have to wait a long time after listening to this talk to actually find that. And the question is, what do we do here and now given what we have seen in ABSORB III 2-year data showing clearly an inferior result."

"Even if you are making important progress with avoiding small vessels, using proper sizing, pre-dilation and post-dilatation, I think it is important to note that, in the current trial as we have it today, the majority of patients did not get the 'PSP.' And the question that comes back to you, and the clinicians, and for all of us, is what do we do with the current patients who have bioabsorbable scaffolds?"

She suggested that until the scaffold is completely gone at 3 years, patients might need to remain on dual antiplatelet therapy (DAPT) "until we know better."

ACC press conference discussant of Hoag Memorial Hospital in Newport Beach, Calif., also saw it as a deterrent to clinical use.

"You can't argue against the data, which is that when you have the gold standard that still has zero thrombosis, it's hard to accept any amount of scaffold thrombosis," she said. "Here I'm going to have to [intravascular ultrasound] all these patients and post-dilate them, so I'm going to do something longer and add to the cost of my procedures. It's hard to palate that. As a clinician, am I going to run out and be implanting more Absorb stents? Probably not."

Even if there are potential long-term benefits, "it's a long time to wait and most of us not quite that patient," she concluded. Ellis noted that superiority is unlikely to emerge at least until after 3 years, and the landmark target lesion failure analysis has been bumped back to between 3 and 7 years' follow-up.

, of Brigham and Women's Hospital in Boston, agreed that there's not much clinical rationale to use these stents with so many other good options, although still reasonable in a clinical trial setting.

Ellis, though, argued that if anything, the findings should "calm the waters," since things weren't as bad as suggested by data from ABSORB 2 and ABSORB JAPAN. "We have enough data that it's not a dangerous device, and we're only going to get more data if we use it," he said at the press conference, after reporters repeatedly questioned his more positive take on the data.

In the trial of 2,008 patients randomized to Absorb or Xience stents, he pointed to an Absorb scaffold thrombosis rate between 1 and 2 years of only 0.3% for a number needed to harm of 317.

And in patients with appropriately sized vessels the difference in target lesion thrombosis was smaller (9.4% vs 7.0%, P=0.11).

Ellis called those numbers very much in line with what would be expected from second-generation device.

"To me the body of emerging data is that the results are narrowing the gap," he said, although in response to a direct question from 乌鸦传媒 on whether the curves were separating at 2 years, he said they were.

Press conference moderator , of Emory University in Atlanta, cautioned that this is just the first generation of bioabsorbable scaffold stents and many others are in the wings, including a next-generation Absorb stent.

"I'm reminded of the time when when we went over to drug-eluting stents," he said. "We...should still try to move the field forward."

Meanwhile, Itchhaporia said, "the people that have already put those in, and [are] sort of thinking about getting rid of dual antiplatelet therapy soon, will pause and rethink whether they need it longer."

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