Polymer-free stents have similar performance profiles, except in diabetes

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Giulio G Stefanini

A pooled data analysis comparing the Cre8 amphilimus-eluting stent (Alvimedica) and the BioFreedom biolimus-eluting stent (Biosensors) demonstrates similar safety and efficacy for the devices, with possible differences in treatment effect for patients with diabetes mellitus. Describing a combined investigation into two multicentre observational studies in Italy in Circulation: Cardiovascular Interventions, the researchers say: “BioFreedom and Cre8 have favourable and comparable safety and efficacy profiles in real-world all-comer patients undergoing percutaneous coronary revascularisation.” Also, they add: “Cre8 might provide a clinical benefit in diabetic patients.”

Polymer-free drug-eluting stents have performed positively in comparisons with bare metal stents and with durable-polymer drug-eluting stents. But to date there have been no direct comparisons of safety and efficacy between different polymer-free drug-eluting stents. The study population came from two single arm studies conducted at 22 Italian centres—the ASTUTE (Amphilimus Italian multicentre registry), and the RUDI-FREE (Polymer free biolimus-eluting stent implantation in all-comers population). ASTUTE enrolled all patients undergoing Cre8 implantation, and RUDI-FREE enrolled all patients undergoing BioFreedom implantation.

The primary endpoint was target lesion failure, defined as a composite of cardiac death, target vessel myocardial infarction, and target lesion revascularisation. Propensity score matching compared safety and efficacy outcomes in 1,280 patients (640 matched pairs) treated with BioFreedom or Cre8.

At one year, target lesion failure occurred in 4% of BioFreedon and 4.2% of Cre8-treated patients (hazard ratio [HR] 0.98, 95% CI 0.57–1.70). Risks of cardiac death (2% vs. 2.1%, HR 1.03, 95% CI 0.47–2.26), target vessel myocardial infarction (0.8% vs. 0.3%, HR 1.89, 95% CI 0.50–6.80), TLR (1.5% vs. 2.2%, HR 0.74, 95% CI 0.34–1.62), and definite/probable stent thrombosis (0.9% vs. 0.8%, HR 1.17, 95% CI 0.36–3.81) were comparable in patients treated with BioFreedom and Cre8. A differential treatment effect by diabetes mellitus status was observed, indicating a benefit of Cre8 in patients with diabetes mellitus (p interaction=0.003).

Summarising the findings, Mauro Chiarito, Giulio G Stefanini (Department of Biomedical Sciences, Humanitas University, Pieve Emanuele-Milan, Italy) and their co-researchers say: “BioFreedom and Cre8 are characterised by a similar performance as indicated by comparable risks of the primary endpoint target lesion failure at one year. Device effectiveness and safety profiles of BioFreedom and Cre8 are similar, as indicated by low and comparable rates of target lesion failure and stent thrombosis at one year.”

They cite the potential benefits of polymer-free drug-eluting stent as an “extremely short” dual antiplatelet therapy duration, which might provide a clinical advantage in the management of patients at high bleeding risk. Moreover, the reduced risk of polymer-related local inflammatory reactions and neoatherosclerosis could lead to a lower risk of thrombotic events over the longer term.

Efficacy and safety was consistent across all major subgroups in the analysis, except for patients with diabetes mellitus: “The observed significant interaction between treatment effects and diabetes mellitus status suggests that the use of Cre8 might be more favourable in patients with diabetes mellitus, and the use of BioFreedom in patients without diabetes.”

This may be accounted for by the method of drug release in Cre8, which has a mixture of sirolimus with long-chain fatty acids, possibly leading to enhanced cellular uptake in patients with diabetes mellitus. But the researchers could not rule out selection bias as the cause.

Among other limitations were baseline imbalances in the matched population despite the use of propensity score-matching, the small sample size which may have led to type II error, and the study was inadequately powered to evaluate rare events such as stent thrombosis.

Chiarito and Stefanini et al point to the optimal performance of BioFreedom and Cre8 in terms of both efficacy and safety. Rates of target lesion failure, its individual components, and stent thrombosis compared favourably with those observed in recent large-scale randomised trials and all-comers registries on other contemporary drug-eluting stents at one-year follow-up. These findings are undoubtedly “reassuring” regarding the use of BioFreedom and Cre8 in everyday clinical practice. Nonetheless, the researchers warn that “any comparisons of event rates between observational and randomised studies should be interpreted with caution”. They say that a propensity score matched analysis “cannot replace an adequately designed randomised trial. Therefore, our findings should be considered as hypothesis generating.”

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