A decade already passed from the first use of bioresorbable vascular scaffold in percutaneous coronary interventions. The first studies - by using surrogate endpoints - showed some superiority of BRS vs. metallic drug-eluting stent in terms of the so-called vascular restoration therapy with recovery of vasomotion and vascular pulsatility when the scaffold was absorbed.
Nevertheless, after these first promising findings, larger and randomized clinical trials and subsequent meta-analyses, powered to hard clinical endpoints, showed that bioresorbable vascular scaffolds, made of poly-lactic polymer, exhibit a higher rate of target lesion revascularization, with in particular a higher rate of scaffold thrombosis as compared with metallic drug-eluting stent. Interestingly, the implantation technique was related to these events rates, as these first-generation bioresorbable scaffolds were characterized by a thick strut (150 micron), which made it similar to first-generation metallic DES and therefore very much dependent by a very precise implantation technique.
At light of these findings, BRS made of polylactic acid were withdrawn from the market and only metallic BRS based on a magnesium platform are still used, restricted to a very specific subset of patients included in controlled studies.
Although BRS use is very limited nowadays, the need of a bioresorbable scaffold for treating coronary lesions, leaving nothing behind and allowing the so-called vascular restoration therapy, is still very much alive.
The FUTURE-II trial is a randomized trial comparing a new, thin-strut bioresorbable scaffold - the FIRESORB -poly-L-lactic acid-based sirolimus-eluting vs. everolimus-eluting cobalt-chromium stent (EES). The FIRESORB scaffold may be defined as a second-generation bioresorbable scaffold: it is made of poly-lactic polymer, but with a strut thickness of only 100-125 micron, which made it close to second-generation drug-eluting metallic stents. The trial wanted to demonstrate non-inferiority of the FIRESORB vs. EES, with a primary surrogate endpoint of late lumen loss at 1-year, which is known to be associated with clinical event rates. Major secondary endpoint is 1-year proportion of covered struts by OCT, which was evaluated in a subgroup of patients.
The trial succeeded to show non-inferiority of FIRESORB vs. EES in terms of 1-year angiographic late lumen loss (0.17 ± 0.27 vs. 0.19 ± 0.37 mm, p for non-inferiority < 0.001). Of note implantation technique was almost perfect in both groups, with a high rate of pre-dilatation and post-dilatation. Non-inferiority was shown also in the secondary OCT endpoints, with a similar proportion of covered struts in both groups; of note a less incomplete strut apposition was found in Firesorb vs. EES group at 1-year, which may be the result of scaffold resorption.
Eventually, no difference was found in terms of target lesion failure between groups with very low rate of events (1.9% vs. 3.3%, p=0.37) and no definite probable device thromboses.
For all these reasons, the results of this trial may revitalize the concept of bioresorbable scaffold or may even stimulate the design of new pivotal studies with this new device. A proper implantation technique together with a device with improved physical and mechanical properties may give the opportunity to have a PLLA-based BRS back in our daily practice in a foreseeable FUTURE.