For a primary composite target-lesion failure outcome, a biodegradable polymer sirolimus-eluting stent showed superiority at 2 years over a durable polymer everolimus-eluting stent in patients undergoing percutaneous intervention (PCI) for an ST-segment elevated acute myocardial infarction (STEMI), according to a late-breaking trial presentation at CRT 2021.
As in the previously reported 1-year results from the BIOSTEMI trial, the advantage of the biodegradable device was “driven by lower rates of target-lesion revascularization,” reported Thomas Pilgrim, MD, of the University of Bern (Switzerland).
Drug-eluting stents have already been established as superior to bare-metal stents, but the question asked in this study is whether the polymer that carries antiproliferative drugs, such as sirolimus or everolimus, improves lesion-based outcomes if it is biodegradable rather than durable, Dr. Pilgrim explained.
The composite primary outcome was target-lesion failure defined by cardiac death, target-lesion MI, or clinically indicated target-lesion revascularization.
After 2 years of follow-up, the rates of target-lesion failure were 5.1% and 8.1% for the biodegradable and durable polymer stents, respectively. This 0.58 rate ratio was statistically significant, favoring the biodegradable stent.
The investigator-initiated BIOSTEMI trial randomized 1,300 patients to one of two drug-eluting stents with ultrathin struts. One was the Orsiro stent that employs a biodegradable polymer to deliver sirolimus. The other was the Xience Prime/Xpedition that uses a durable polymer stent to deliver everolimus.
The strut thicknesses of the Orsiro stent are 60 mcm for stents of 3.0 mm in diameter or smaller and 80 mcm for those with a larger diameter. The strut thickness of the Xience stent is 81 mcm regardless of diameter.
“Patients with an acute myocardial infarction are at increased risk of stent-related events due to exacerbated inflammatory response and delayed arterial healing,” Dr. Pilgrim said. The theoretical advantages of polymer that biodegrades include “mitigation of the arterial injury, facilitation of endothelialization, and reduced intimal hyperplasia,” he explained at the meeting sponsored by MedStar Heart & Vascular Institute.
The rates of cardiac death (2.9% vs. 3.2%) and target-vessel MI (2.9% vs. 3.2%) were lower for the biodegradable polymer stent, but not significantly. However, the rates of target-vessel revascularization at 2 years were 2.5% versus 5.1%. The associated rate ratio of 0.52 favoring the biodegradable stent was significant.
Similar results favoring the biodegradable polymer stent were observed at 1 year, but those earlier results factored in historical data from the BIOSCIENCE trial, using a Bayesian analysis, to improve the power of the comparison. In this 2-year analysis, the superiority of the biodegradable polymer stent to the durable polymer stent remained statistically significant even when excluding those historical controls.
The advantage of the biodegradable polymer stent was confined to “device-oriented” outcomes, according to Dr. Pilgrim. When compared for important patient-oriented outcomes at 2 years, there were no significant differences. Rather, several were numerically more common, including death (4.2% vs. 3.8%) and MI (3.7% vs. 3.1%) in those who were randomized to the biodegradable polymer stent.
But these types of clinical outcomes are not necessarily related to stent assignment because “up to one-half of all events over the 2 years of follow-up were unrelated to the stent implanted,” Dr. Pilgrim said. He noted that high rates of events unrelated to the implanted stent have also been seen in follow-up of other comparative stent trials.
The superiority of the biodegradable stent is noteworthy. Although Dr. Pilgrim described the BIOSTEMI trial as “the first head-to-head comparison of two new-generation drug-eluting stents in patients undergoing a primary percutaneous intervention for acute myocardial infarction,” there have been several studies comparing stents for other indications. Significant differences have been uncommon.
Dr. Sripal Bangalore
“Over the last 10 years, we have seen a number of noninferiority stent trials, but only now are we seeing some superiority differences. This is a move in the right direction,” commented Sripal Bangalore, MD, director of the cardiovascular outcomes group, New York University.
However, he, like others, questioned whether the difference in outcomes in this trial could be fully attributed to the type of polymer. He noted that all stents could be characterized by multiple small and large differences in design and composition. Any specific characteristic, such as biodegradable polymer, might be an important contributor but not an isolated factor in the outcomes observed.
On the day that the 2-year results of the BIOSTEMI trial were presented at the CRT 2021 meeting they were simultaneously published in JACC: Cardiovascular Interventions.
Dr. Pilgrim reports financial relationships with several companies that make stent devices, including Biotronik and Boston Scientific. Dr. Bangalore reports no potential conflicts of interest.