PRISON IV: Biodegradable-Polymer Stent Fails to Secure Parity in Chronic-Occlusion PCI

Patrice Wendling

November 04, 2016

WASHINGTON, DC — The Orsiro sirolimus-eluting stent with a biodegradable polymer (Biotronik) was unable show similar in-segment late lumen loss in a randomized comparison against the durable-polymer Xience Prime/Xpedition everolimus-eluting stents (Abbott Vascular) in patients with successfully recanalized chronic total occlusions (CTOs)[1].

Nine-month angiographic follow-up from PRISON IV showed Orsiro not only missed this primary noninferiority end point vs Xience (0.13 mm vs 0.02 mm; noninferiority P=0.11) but also had a significantly higher rate of binary restenosis (8.0% vs 2.1%; P=0.028).

The findings, reported at TCT 2016 and published online in JACC Cardiovascular Interventions, are disappointing for the Orsiro stent after researchers reported angiographic results comparable to Xience Prime in simple de novo lesions in BIOFLOW II and similar outcomes to two other stents in an all-comers population in BIORESORT.

Dr Koen Teeuwen

Principal investigator Dr Koen Teeuwen (St Antonius Hospital, Nieuwegein, the Netherlands) told heartwire from Medscape, "This is a more complex population, and that's the only thing that may be the cause of the difference. Still, I also have to note these differences are not that big; overall, the study results are very good."

He added, "But if I would have to choose or advise, I would still use the Xience stent for this selected population."

Speaking with the media, Dr Jonathan Hill (London Bridge Hospital, UK) said, "These were not the most complex CTOs being treated, J-CTO [scores] 1 and 2, but what I think this trial again demonstrates is the high performance of the [everolimus-eluting stent] with persistent polymer.

"I don't think it really puts the biodegradable, disappearing polymer story further forward, it just reinforces that we already have a high-performing platform."

Following the formal presentation, panelist Dr Wojtek Wojakowski (Medical University of Silesia, Katowice, Poland) struck a similar note, describing the overall results as "extremely good" and the late lumen loss of just 0.02 mm with Xience "particularly impressive" given the complexity of CTO lesions and a total stent length of around 52 mm in both groups.

Teeuwen noted that there were no significant differences in stent sizes or restenosis rates whether recanalization was done retrograde or antegrade.

He added that results of a substudy in 60 patients in whom optical coherence tomography imaging are also being analyzed to dig into the mechanisms of restenosis and whether there were any differences in stent sizes, given the differences in strut thickness between the Xience (81 µm) and Orsiro (60 µm for stent diameters <3.0 mm and 80 µm for stents >3.0 mm).

Overall, the study involved 330 consecutive patients evenly randomized to the two stents, with 9-month angiographic follow-up available in 85% and 12-month clinical follow-up in 99%.

Clinical events were comparable between the Orsiro and Xience groups, including clinically driven target lesion revascularization (9.2% vs 4%), target vessel failure (9.9% vs 6.6%), or major adverse cardiac events (9.9% vs 5.3%), but Teeuwen noted that the study was not powered for clinical end points.

While several discussants praised the excellent results in both groups, some questioned the study design, including the wisdom of doing the angiographic end point first, because such evaluations can induce clinical events; and whether the primary end point was "almost biased" using a marker of 9-month late luminal loss, because the effect of a biodegradable polymer would likely be seen later.

Asked what clinicians should take away from the findings, Teeuwen told heartwire , "We need selected technology to reduce events because these are really long stented tracts; these are lesions that need high radial force; however, we also know from our earlier studies with Cypher stents in CTOs that they also have a high rate of adverse events, so thin struts are also needed to reduce late adverse events."

The study was supported by grants from Biotronik and Abbott Vascular. Teeuwen reported no relevant financial relationships. Disclosures for the coauthors are listed in the paper. Hill reported consultant fee/honoraria/speaker's bureau from Abbott Vascular, Abiomed, Boston Scientific and St Jude Medical.

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