Previous clinical trials suggested that ultra-thin strut biodegradable polymer sirolimus-eluting stent (BP-SES) may be associated with lower target lesion failure (TLF) when compared to durable polymer everolimus-eluting stents (DP-EES). However, the possible underlying mechanisms remain unclear. Therefore, the all-comers CASTLE study was designed to assess the role of imaging-guided percutaneous cardiac intervention (PCI) in the clinical outcomes difference between BP-SES vs DP-EES.
BP-SES has ultra-thin struts (60μm) and a biodegradable polymer that may provide potential advantages such as reduced vessel inflammation and thrombogenicity. Randomised clinical trials have provided mixed results. The BIOFLOW-V and BIOSTEMI trial showed a lower risk of TLF with BP-SES when compared to DP-EES. Meanwhile, the BIOSCIENCE trial showed neutral results. One of the possible explanations of these contradictory findings is the use of intracoronary imaging. The CASTLE investigator hypothesised that under imaging-guidance PCI, the actual difference in clinical outcomes between BP-SES and DP-EES might be clarified.
The CASTLE study is an investigator-initiated, multicentre, single-blinded, randomised, non-inferiority clinical trial executed in 69 centres in Japan. The population was composed of patients with acute and chronic coronary syndromes. Patients were randomised in a 1:1 ratio to image-guided PCI (intravascular ultrasound or optical coherence tomography) with BP-SES (intervention group) or DP-EES (control group). The primary outcome was TLF (cardiovascular death, target vessel myocardial infarction, and clinically driven target lesion revascularisation) at 12-month follow-up. An independent clinical event committee evaluated angiographies and clinical events. The prespecified margin for non-inferiority was 3.3%.
The investigator reported an interim analysis with ~70% of the follow-up. Between May 2019 and March 2020, 1440 patients were randomised; 722 were allocated to BP-SES and 718 to DP-EES. The 12-month follow-up was completed in 69.1% in the BP-SES group and 68.6% in the DP-EES. There were no significant differences between groups in terms of clinical and procedural characteristics. The trial included mainly chronic coronary syndromes (85%), stent diameter ? 3mm (66%), and imaging-guidance was performed in at least 97.5% of the patients. At 30-day follow-up, there was no difference in TLF between DP-SES vs DP-EES (5.0% vs 4.9%) or its components. In the primary endpoint, at 12-month follow-up, there was no difference in TLF between DP-SES vs DP-EES (HR 0.59 [95%CI 0.26 to 1.36]).
At least in this interim analysis, the data suggest that BP-SES and DP-EES may have similar clinical outcomes when PCI is performed under intracoronary imaging guidance. However, we should cautiously wait until the complete follow-up is performed to assess any potential difference between these two devices.