PRISON IV Trial Evaluates Biotronik’s Osiro Biodegradable SES to Treat CTOs
November 2, 2016—The randomized multicenter PRISON IV trial evaluated Biotronik’s hybrid, ultra-thin strut Osiro sirolimus-eluting stent (SES) with a biodegradable polymer compared to Abbott Vascular’s thin-strut Xience everolimus-eluting stent (EES) with a durable polymer. In the trial, the Osiro SES failed to show noninferiority compared to Xience EES in terms of in-segment late lumen loss (LLL) in successfully treated chronic total occlusions (CTOs). In addition, although the rate of binary restenosis was low overall in this complex lesion subset, it was higher with the Osiro SES compared with the Xience EES.
Findings from the PRISON IV trial were presented as a First Report Investigation at TCT 2016, the 28th annual Transcatheter Cardiovascular Therapeutics scientific symposium in Washington, DC. The study was also published online by lead investigator Koen Teeuwen, MD, et al in the Journal of the American College of Cardiology: Cardiovascular Interventions. The PRISON IV trial was funded by unrestricted research grants from Biotronik and Abbott Vascular.
Dr. Teeuwen explained that treating CTOs can be challenging because of their long lengths and the presence of greater degrees of calcium, often requiring long stents with high radial strength to maintain acute gain and minimize late vessel recoil after percutaneous coronary intervention (PCI).
As summarized in the TCT press release, the study enrolled 330 consecutive patients with successfully recanalized native total or chronic total coronary occlusions between February 2012 and June 2015. Patients were randomized to the hybrid SES or the EES in two Belgian and six Dutch high-volume PCI centers.
The primary noninferiority endpoint was in-segment LLL assessed at 9 months by angiography.
Secondary angiographic endpoints included in-stent LLL, minimal lumen diameter, in-stent and in-segment percentage of diameter stenosis, binary restenosis, and reocclusions at 9 months. Secondary individual and composite clinical endpoints were clinically indicated target lesion revascularization (TLR)/target vessel revascularization (TVR), myocardial infarction, death (cardiac and noncardiac), stent thrombosis, target vessel failure, and major adverse cardiac events (MACEs).
Follow-up angiography was performed at 9 months after the procedure, and clinical follow-up was performed during the hospital stay and at 1, 6, 9, and 12 months.
At 9 months, angiography was available in 281 of 330 (85%) patients.
The primary noninferiority endpoint of in-segment LLL was not met for SESs compared with EESs (0.13 ± 0.63 mm vs 0.02 ± 0.47 mm; P = .08, two-sided; difference = 0.11 mm; 95% confidence interval, -0.01 to 0.25; Pnoninferiority = .11, one-sided).
For secondary endpoints, in-stent LLL was comparable between SESs and EESs (0.12 ± 0.59 vs 0.07 ± 0.46 mm; P = .52). The incidence of in-stent/in-segment binary restenosis was higher with SESs versus EESs (8% vs 2.1%; P = .028), with comparable rates of reocclusions (2.2% vs 1.4%; P = .68). Clinically indicated TLR and TVR (9.2% vs 4%; P = .08 and 9.2% vs 6%; P = .33), target vessel failure (9.9% vs 6.6%; P = .35) and definite or probable stent thrombosis (0.7% vs 0.7%; P = 1.0) were comparable in the SES and EES groups.
Clinical follow-up at 12 months was available in 99% of all patients.
Clinically indicated TLR and TVR, target vessel failure, and MACEs were comparable between both groups. Two patients in the SES group received nonclinical TLR with balloon angioplasty after severe stent strut malapposition was observed with optical coherence tomography at 9 months. There was one probable or definite stent thrombosis in each stent group (0.7% vs 0.7%; P = 1.0).
Dr. Teeuwen concluded that the findings of the study show that the noninferiority of in-segment LLL was not met for SESs as compared with EESs in successfully recanalized CTOs. In addition, the rate of binary restenosis was significantly higher with SESs. Future developments in stent technology should focus on the challenging characteristics of CTOs to improve device efficacy and clinical outcomes.