Good Long-term Results With FANTOM BVS, but More Data Needed

New long-term follow-up of patients treated with a thin-strut, second-generation bioresorbable vascular scaffold (BVS) point to some signs of life for the beleaguered technology, with investigators reporting low rates of major adverse cardiovascular events and target vessel failure at 5 years.

Among 240 patients treated with the Fantom BVS (Reva Medical), there were just three cases of definite/probable stent thrombosis at 5 years. Of these, one occurred in the subacute phase (2-30 days) and the other two occurred beyond 1 year. There were no reports of definite/probable stent thrombosis between 3 and 5 years, lead investigator Matthias Lutz, MD (Universitätsklinikum Schleswig-Holstein, Kiel, Germany), reported online this week as part of a sneak peek at TCT 2021.

Ziad Ali, MD (St. Francis Hospital and Heart Center, Roslyn, NY), who moderated the abstract session, said the long-term FANTOM II findings are thought-provoking, but he harkened back to an earlier era when there was genuine excitement surrounding the Absorb BVS (Abbott Vascular). This excitement was at least tempered, if not outright squashed, in light of an avalanche of negative data from the ABSORB clinical trials and other studies.

Still, Ali said the current stent technology, as good as it is, has drawbacks. “We can’t deny that drug-eluting stents have a 2% per year attrition rate, and as a result I really do think there is a market for [bioresorbable scaffolds],” he said. “My biggest question is how do we reinvigorate the field to be interested in doing this type of work?”

Lutz said that for the field to progress, it had to address the major issues uncovered in the ABSORB trials with the first-generation BVS. For one, the Fantom device has thinner struts, an upgrade that doesn’t compromise radial strength. Second, imaging with optical coherence tomography (OCT) showed almost complete strut coverage with Fantom at 9 months. Lutz is hopeful that positive data from FANTOM II will “stabilize the field,” though he also emphasized that operators using BVS still need to practice good techniques, including predilatation and use of either IVUS or OCT to facilitate implantation.

Absorb’s Shadow Looms Large

The high-profile failure of Absorb is well documented, with several studies showing the BVS was associated with a significantly increased risk of target lesion failure and device thrombosis. The US Food and Drug Administration eventually warned physicians about higher risks of MACE with Absorb and Abbott stopped making the scaffold because of low commercial sales. Subsequently published 5-year results from ABSORB III showed that while the cumulative risk of TLF, target-vessel MI, and scaffold thrombosis remained higher with BVS, that excess risk stabilized between 3 and 5 years.

The Fantom sirolimus-eluting device is a second-generation bioresorbable scaffold with relatively thin struts (125 µm) that has received CE Mark approval in Europe.

In the FANTOM II trial, investigators implanted the BVS in 240 patients (70.4% men; mean age 62.7 years) across 28 European centers, as well as some from Brazil and Australia. The study population consisted of stable CAD patients with a single lesion ≤ 20 mm in length with a vessel diameter of 2.5 to 3.5 mm. Nearly three-quarters of patients had hypertension, 70.8% had hyperlipidemia, and 23.8% had diabetes. Roughly half of patients had a lesion in the left anterior descending artery, 31.3% in the left circumflex artery, and 20.2% in the right coronary artery.   

At 5 years, the primary composite endpoint of MACE had occurred in 5.8% of patients. The respective rates of cardiac death, all MI, and clinically driven TLR were 1.7%, 1.7%, and 2.9%. TLF, which included cardiac death, target-vessel MI, and clinically driven TLR, was reported in 5.4% of patients. Over time, said Lutz, the MACE and TLF event curves were relatively flat from 24 months onward.

Michael Haude, MD, PhD (Rheinland Klinikum Neuss, Germany), one of the discussants, said the interventional community needs a “reset” with respect to BVS technology. The newer devices have better mechanical properties and thinner struts, he said, “but nevertheless, all the things we did at the time of Absorb, we have to do again. The question we have to ask ourselves is if there is still a clinical need for the device now that we have ultrathin, permanent drug-eluting stents that do a supergood job. I still believe there is a need for it, but again we have to show first that these devices are safe.”

For his part, Lutz also sees a role for the technology, if maybe a limited one.

“Complex lesions and bifurcations, I think it’s very hard to work with these devices,” said Lutz. “The biggest advantage, for example, may be lesions in young patients and very long lesions. Before, caging a whole right coronary artery with metal in a 30- or 40-year-old patient, using this device would be much better for a very long life span.”

Right now, investigators are currently enrolling up to 1,500 patients in the Fantom European postmarketing trial, and 1- and 2-year results are expected in 2022 and beyond.

The third-generation Fantom Encore BVS, a device with struts even thinner than the one used in FANTOM II, has already received CE Mark approval in Europe. Depending on the size of scaffold, the struts range in thickness from 95 to 115 µm. In contrast, the first-generation Absorb bioresorbable scaffold had a strut thickness of 157 µm, while Magmaris (Biotronik), which also has CE Mark approval, has struts 166 µm thick. Lutz said the Fantom Encore has the same radial strength as the earlier device.