ABSORB II: Bioresorbable scaffold outcomes comparable to DES at 1 year

WASHINGTON — The Absorb bioresorbable scaffold demonstrated overall clinical outcomes comparable to those of the Xience everolimus-eluting stent in treating CAD, according to 1-year results from the ABSORB II trial presented at a late-breaking session of TCT 2014.

Perspective from David G. Rizik, MD

Additionally, the researchers reported a significant reduction in 1-year cumulative angina episodes with the Absorb scaffold (Abbott Vascular), although the mechanism for this finding is unknown.

Principal investigator Patrick W. Serruys, MD, professor of interventional cardiology at the Thoraxcentre, Erasmus University Hospital, Rotterdam, The Netherlands, presented the data from ABSORB II, the first prospective, randomized controlled trial comparing the safety and efficacy of the Absorb bioresorbable scaffold with the Xience family of DES (Abbott Vascular).

The study evaluated an intent-to-treat population of 501 patients with CAD, who were randomly assigned to undergo treatment with the Absorb bioresorbable vascular scaffold (BVS; n=329) or the Xience metallic DES (n=164).

At 1 year, the study retained 98.2% of the original Absorb intent-to-treat cohort and 98.8% of the Xience cohort. Success rates of the two devices, which mainly consisted of B1/B2 lesions, were comparable (Absorb device success, 99% vs. Xience, 100%). There was significantly lower acute gain in the Absorb arm vs. the Xience arm, as imaged through angiography (Absorb, 1.15 ± 0.4 mm vs. Xience, 1.46 ± 0.4 mm; P<.001) and IVUS (Absorb, 2.9 ± 1.3 mm² vs. Xience, 3.6 ± 1.3 mm²; P<.001).

“This difference is not related to the acute recoil measured immediately after the device implantation, which was 0.19 in both arms, but could be attributed to the difference in pressure … during the post-implantation dilatation performed in a similar proportion (approximately 60%) of patients in each arm,” Serruys said during the press conference.

Serruys reported two scaffold thromboses, one acutely within 24 hours of the procedure and a second that occurred subacutely on day 2. He said the first case involved a protocol violation.

“This was a violation that involved treating a bifurcation not allowed by protocols,” he said.

The 1-year rates of the patient-oriented clinical endpoint of all-cause death, MI and revascularization were 7.3% for Absorb and 9.1% for Xience (P=.47). In terms of the device-oriented clinical endpoint, defined as target lesion failure, the 1-year rates were 4.8% for Absorb and 3% for Xience (P=.35) patients. There were also comparable rates of the individual constituents of these endpoints between the two cohorts.

Although the two arms had similar exercise performance and angina statuses as determined by the Seattle Angina Questionnaire, there was a difference in 6-month nitrate use (Absorb, 17.8% vs. Xience, 26.7%; P=.02) and a trend toward a difference in 12-month nitrate use (Absorb, 19.5% vs. Xience, 26.2%; P=.09).

Notably, patients in the Absorb arm had a significantly lower cumulative rate of angina at 1 year than those in the Xience arm (21.8% vs. 30.5%; P=.04). When angina events during the first 7 days of hospitalization were excluded, the 1-year rates were 16.4% in the Absorb arm vs. 25.6% in the Xience arm (P=.015), based on adverse event recording.

The ABSORB II trial’s primary endpoint is vasomotion at 3 years, and results will be evaluated annually up to 3 years.

Serruys said although the current findings are preliminary, they are heartening.

“The good news is that in terms of events, we are doing well,” he said. “As a matter of fact, the patient-oriented composite endpoint is somewhat lower [with] Absorb.”

He said one concern thus far has been investigator hesitancy in terms of deploying the device.

“When we start these trials, the investigators are somewhat afraid of the fragility of the polymers, so they restrain themselves from using the whole pressure and volume of the balloon,” he said. “This is something we have corrected; we know that the presentation of the lesion has to be impeccable, and then the scaffold will deploy easily.” – by Jennifer Byrne

For more information:

Serruys PW. Plenary Session XII: Late-Breaking Clinical Trials No. 2. Presented at: TCT 2014; Sept. 13-17, 2014; Washington, D.C.

Disclosure: Serruys reports no relevant financial disclosures.

Perspective

David G. Rizik, MD

The ABSORB II trial is the birthplace of high-level science for bioresorbable stents and goes a long way toward reassuring us that our enthusiasm, from a safety perspective, is warranted. There have recently been retrospective analyses — with lower levels of evidence — that have suggested concerns over safety. ABSORB II is another step toward putting these safety concerns to rest. There was no significant increase in stent thrombosis, according to the protocol, and there was no significant increase in periprocedural MI. In particular, I found the reduction in angina at 1 year to be most compelling. Earlier, we saw the EXTEND trial, in which Dr. Alexandre Abizaid compared the Absorb in 250 patients to a similar cohort treated with the best-in-class DES. What he noted was a very similar reduction in angina compared to the best-in-class DES. This is very important, because this is the gold standard; there is not a safer, more efficacious stent [than Xience]. While a reduction in chest pain is important on its own, I think these findings will have even more far-reaching implications. This could mean better performance on noninvasive testing, and a possible reduction in anginal medications, which is certainly going to be cost savings for insurers. It may also mean a reduction in hospitalizations and repeat procedures.

David G. Rizik, MD

Chief Scientific Officer

Director, Cath Lab Services

Scottsdale Lincoln Health Network, Scottsdale, Arizona

Disclosures: Rizik reports no relevant financial disclosures.