TCT.15: Absorb scaffold is noninferior to Xience stent at 1 year

After one year, 7.8 percent of patients with myocardial ischemia who underwent PCI and received the investigational Absorb everolimus-eluting bioresorbable vascular scaffold had target-lesion failure compared with 6.1 percent of patients who received the Xience everolimus-eluting cobalt-chromium stent, according to a multicenter, randomized study.

The results of the ABSORB III trial were within the prespecified margin for noninferiority with regards to the primary end point of target lesion failure, which researchers defined as cardiac death, target-vessel MI or ischemia-driven target-lesion revascularization.

Study author Dean J. Kereiakes, MD, medical director of the Christ Hospital Heart & Vascular Center and The Lindner Research Center in Cincinnati, presented the findings on Oct. 12 in a late-breaking clinical trial session at the Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium in San Francisco.

Results were simultaneously published online in the New England Journal of Medicine. Abbott Vascular, the manufacturer of the Absorb scaffold and the Xience stent, funded the study. The FDA has approved the Xience stent. The Absorb scaffold is not yet FDA-approved, but was approved in Europe in 2011.

In the prospective, single blind trial, the researchers randomized 2,008 patients at 193 sites in a 2:1 ratio to receive the Absorb scaffold or the Xience stent. At baseline, the groups were well balanced. Within 24 hours before the PCI procedure, all patients received at least 300 mg of aspirin. They also received a loading dose of a P2Y12 receptor antagonist before the procedure or within an hour after the procedure.

The mean age of patients was roughly 64, approximately 70 percent of patients were male and approximately 88 percent were white.

After a year, the rates for cardiac death (0.6 percent in the Absorb group versus 0.1 percent in the Xience group), target-vessel MI (6.0 percent versus 4.6 percent) and ischemia-driven target-lesion revascularization (3.0 percent versus 2.5 percent) were similar between the groups.

The secondary end points of angina (18.3 percent versus 18.4 percent), all revascularization (9.1 percent versus 8.1 percent) and ischemia-driven target-vessel revascularization (5.0 percent versus 3.7 percent) were also not statistically significant between the groups.

The rates of early (0 to 30 days) device thrombosis were 1.06 percent and 0.73 percent, while the rates of late (past 30 days to one year) device thrombosis were 0.46 percent and 0 percent, respectively. At one year, the definite device thrombosis rates were 1.38 percent and 0.74 percent, while the probable device thrombosis rates were 0.15 percent and 0 percent, respectively.

Kereiakes said Abbott is enrolling an additional 3,000 patients in the ABSORB IV trial, so Abbott will eventually have data on approximately 5,000 patients from the ABSORB III and IV studies with a primary end point of target-lesion failure from one to five years.

“I think that’s the quote ‘money shot’ to show that there’s clinically meaningful differences between these two devices,” Kereiakes said. “The problem with that is it takes probably six, seven years before we see those results. To not have the technology available, how long can or should people wait before they have this technology available? If we did this for every device, I think it would be very problematic for the American public.”

The Absorb scaffold is not a metallic stent and is designed to improve late outcomes in patients compared with permanent metallic stents. Daniel I. Simon, MD, division chief of cardiovascular medicine at UH Case Medical Center in Cleveland, said that even the best-in-class drug-eluting stents have patient-related event rates at five years of 16 percent to 17 percent, of which approximately half are device-related.

“We just have this need that we’re trying to do better for our patients,” Simon said. “This is another tool in the toolbox to try to address the long-term out to the five-year point. As Dean says, we need time.”

Robert A. Byrne, MB, BCh, PhD, cardiologist at the German Heart Centre in Munich, wrote in an accompanying editorial that the noninferiority margin was large and that the clinical relevance of noninferiority was open to question. He also noted that the trend toward higher rates of target-lesion failure in the Absorb group was noteworthy and that definite or probable stent thrombosis was twice as likely in patients in the Absorb group.

“Although the concept of self-degrading stents is intuitively attractive, promise alone is not enough to make us unconditionally embrace this technology,” Byrne wrote. “For the moment, the trends toward higher event rates with the Absorb scaffold and the additional challenges associated with implantation must be considered. Against this backdrop, the advantages of the Absorb scaffold must be evident and tangible; otherwise, acceptance of these limitations will not be broad.”