Abstract 32: Per Protocol versus Intent-to-treat Analysis in a Non-inferiority, Randomized Trial of the Safety and Efficacy of the Penumbra 3D Stent Retriever as an Adjunct to Aspiration in Acute Ischemic Stroke

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Abstract

Introduction: The relative treatment effects for a stent retriever when used as an adjunct to aspiration versus aspiration alone remain unclear. The aim of this study was to demonstrate the safety and efficacy of the Penumbra stent retriever, 3D, when used in conjunction with the Penumbra Aspiration System (3D/PS), was non-inferior to the Penumbra Aspiration System (PS) alone. It remains controversial if a Per Protocol (PP) or an Intent-To-Treat (ITT) analysis is more appropriate for this study design.

Hypothesis: PP and ITT analyses are comparable for a non-inferiority design trial.

Materials and Methods: Patients presenting with symptoms of ischemic stroke within 8 hours of onset who had evidence of a LVO (diameter ≥2.5mm) and a NIH Stroke Scale ≥8 were assigned 1:1 to either treatment group. The primary endpoint for effectiveness was angiographic revascularization of the occluded target vessel at immediate post-procedure where the 3D/PS is non-inferior to PS by no more than 15%. Key secondary endpoints were 90 day functional independence as defined by a modified Rankin score 0-2, all-cause mortality and the incidence of symptomatic intracerebral hemorrhage. A Core Laboratory assessed imaging data.

Results: The trial was terminated in June 2016 after the DSMB voted unanimously that recruiting additional subjects was judged to be both not feasible and unable to alter conclusions. A total of 198 patients were randomized at 25 sites: 98 to the 3D/PS and 100 to the PS alone group. The results indicate the 3D/PS was non-inferior to the PS alone in safety and effectiveness (difference in TICI 2-3=2.6%, 95%CI -5.8 to 11%). PP and ITT analyses showed similar results (Table).

Conclusion: This is the first Class 1 evidence showing the similarity in safety and effectiveness of a stent retriever when used as an adjunct to aspiration versus aspiration alone in acute stroke from LVO. Both PP and ITT analyses showed similar results.

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