TRANSFORM-OCT: Similar Early and Late Healing With Bioresorbable- and Durable-Polymer DES

WASHINGTON, DC—A head-to-head comparison of the Synergy everolimus-eluting stent with a bioresorbable polymer and the Resolute Integrity zotarolimus-eluting stent with a durable polymer showed both stents had similar early and late healing responses when assessed by optimal coherence tomography (OCT).

The 18-month follow-up result, an assessment of in-stent neoatherosclerosis, was not statistically different between Synergy (Boston Scientific) and Resolute Integrity (Medtronic), missing the primary endpoint. For investigators, though, the findings speak to the strength of current-generation drug-eluting stents rather than to a failure of the bioresorbable-polymer device to reduce the development of neoatherosclerosis.

“At this point, there is no evidence of any type of additional benefit of the bioresorbable polymer, but what I think is important to keep in mind is that the level of healing at 18 months was impressively good with the current-generation stent,” lead investigator Giulio Guagliumi, MD (ASST Papa Giovanni XXIII, Bergamo, Italy), told TCTMD. “Whether the polymer is bioresorbable or durable, when it is biocompatible it is going to have a favorable impact on healing.”

Davide Capodanno, MD (University of Catania, Italy), one of the study authors, made a similar comment, telling TCTMD that the rate of neoatherosclerosis observed with Resolute Integrity at 18 months is reassuringly low and a lower rate than expected based on past studies.

“Also, both stents investigated showed excellent coverage rates with a limited volume of mature neointima,” he said. “Interestingly, we did not find significant differences between the two devices, which are different for a number of reasons, including strut thickness, polymer, and drug. Overall, the study adds mechanistic insight into the reason why latest-generation drug-eluting stents represent such a good standard nowadays.”

Presenting the results of the TRANSFORM-OCT study at TCT 2016, Guagliumi said one of the mechanisms implicated in late stent failure is the development of atherosclerosis within the neointimal tissue. To mitigate the risk of durable polymers, which have been suggested to delay healing and increase the risk of neoatherosclerosis, stents with bioresorbable polymers have been developed. OCT has a high degree of accuracy for the detection of strut coverage, as well as components of neoatherosclerosis, such as lipid-laden neointima, macrophage infiltration, in-stent calcification, and neoatherosclerotic plaques, said Guagliumi.

Biocompatibility of Polymer Is Key

In the present study, the researchers randomized 90 patients with multivessel coronary artery disease undergoing staged PCI of two or more coronary arteries. Patients, including a large percentage who had ACS, received treatment with the Synergy everolimus-eluting stent with the bioresorbable-polymer or the Resolute Integrity zotarolimus-eluting stent with a durable polymer. All patients underwent serial OCT imaging pre- and poststenting, as well as at 3 and 18 months.

Quantitative data at 3 months showed comparable rates of maximal uncovered stent lengths between Synergy and Resolute Integrity, a coprimary endpoint of the trial. At 3 months, approximately 80% of the struts were covered, although there was wide variability between patients. Additionally, the percentage of uncovered struts and that of uncovered struts fully apposed were similar in patients who received the Synergy and Resolute Integrity stents.

At 18 months, the percentage of patients with evidence of in-stent neoatherosclerosis was 11.6% among patients treated with the bioresorbable-polymer everolimus-eluting stent and 15.9% among patients treated with the durable-polymer zotarolimus-eluting stent. Powered for superiority between the two stent types, the 18-month coprimary endpoint was not statistically significant (P =0.59). Overall, the percentage of OCT frames with neoatherosclerosis was 1.1% and 2.5% in patients who received the Synergy and Resolute Integrity stents, respectively (P = 0.33).

To TCTMD, Guagliumi said pathology studies have shown that neoatherosclerosis occurs later in patients treated with a bare-metal stent than in those with a drug-eluting stent, but one recent review suggested neoatherosclerosis occurring between 1 and 3 years is evident in as many as 50% of patients with a drug-eluting stent. The documentation of neoatherosclerosis in TRANSFORM-OCT was “extremely sensitive,” he added, measured in just one or two frames. Despite this, the “phenomenon was much lower than what we were expecting based on pathology,” said Guagliumi.

The bottom line, he said, is the trial provides very reassuring evidence of “stent acceptance” in the long term. “Do we need it?” asked Guagliumi, referring to bioresorbable-polymer drug-eluting stents. “I don’t have the answer,” he said, “but we can obtain similar results and very reassuring results with two different stent technologies.”

Jonathan Hill, MD (London Bridge Hospital, England), one of the panelists during the morning press conference, said the 18-month results don’t dampen enthusiasm for the bioresorbable polymer but confirm that drug-eluting stents with a bioresorbable polymer perform extremely well when compared with current stents on the market. “We’ve moved on from the more ‘bio-unfriendly’ persistent polymers,” he said. “I think what we’re comparing here is biofriendliness, or biocompatibility, and polymers that completely disappear.”