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Updated: Jan 9, 2026
Optimized Management of Endovascular Treatment for Acute Ischemic Stroke
Published on: January 18, 2018
Understanding non-inferiority trials: Lessons from trials comparing thrombectomy with or without intravenous
William Boisseau1, Tim E Darsaut2, Jean Raymond3
1Interventional Neuroradiology Department, Rothschild Foundation Hospital, Paris, France.
Background:
Non-inferiority (NI) trials are essential to evaluate whether new treatments which may offer some collateral benefit (such as less invasiveness, fewer side effects, availability, ease of administration, or lower cost) do so without significant loss of efficacy, as compared to treatments that are already established to be beneficial. NI trials pose specific design challenges, such as selecting appropriate NI margins, as well as unique problems of interpretation.
Methods:
We examine six NI trials that compared thrombectomy with or without intravenous thrombolysis (IVT). We review fundamental problems with NI trials.
Results:
Two of six trials reported that thrombectomy alone was non-inferior compared to thrombectomy combined with IVT. These trials used large NI margins or stopped recruitment prematurely after an interim analysis. The remaining four trials failed to demonstrate non-inferiority. In general, the chosen NI margins were unjustified and clinically unacceptable. A meta-analysis showed NI at a 10% margin, but not at a clinically pertinent 5% level. We examine (i) assay sensitivity, (ii) the constancy assumption and (iii) NI margins, three concepts that are crucial to understand NI trials. We question whether NI trials are appropriate in acute stroke, where there is little room to accept inferiority. Assessing superiority regarding surrogate outcome measures that have shown a causal relationship with clinical outcomes may be an alternative approach.
Conclusion:
Thrombectomy alone has not properly been shown non-inferior to thrombectomy with IVT. The NI trial design is poorly adapted for use in acute stroke.
Insights
Non-inferiority trials comparing thrombectomy alone to thrombectomy with intravenous thrombolysis (IVT) in acute stroke are problematic. Current evidence does not adequately support thrombectomy alone as non-inferior to combination therapy.
Area of Science:
- Neurology
- Clinical Trials
- Medical Research
Background:
- Non-inferiority (NI) trials assess new treatments with potential benefits (e.g., fewer side effects, lower cost) against established treatments without significant efficacy loss.
- NI trials present unique design and interpretation challenges, including selecting appropriate non-inferiority margins.
Purpose of the Study:
- To examine six non-inferiority trials comparing thrombectomy with or without intravenous thrombolysis (IVT) in acute stroke.
- To review fundamental problems and concepts crucial to understanding NI trials, such as assay sensitivity, constancy assumption, and NI margins.
Main Methods:
- Review of six non-inferiority trials comparing thrombectomy alone versus thrombectomy with IVT.
- Analysis of trial design, non-inferiority margins, and statistical outcomes.
- Examination of concepts like assay sensitivity, constancy assumption, and non-inferiority margins.
Main Results:
- Two of six trials found thrombectomy alone non-inferior to thrombectomy with IVT, often due to large margins or premature stopping.
- Four trials failed to demonstrate non-inferiority, with generally unjustified and clinically unacceptable margins.
- A meta-analysis showed non-inferiority at a 10% margin but not at a clinically relevant 5% margin.
Conclusions:
- Thrombectomy alone has not been adequately demonstrated as non-inferior to thrombectomy with IVT in acute stroke.
- The non-inferiority trial design appears poorly suited for acute stroke treatment evaluation.
- Assessing superiority using surrogate outcomes with established clinical relevance may be a more appropriate alternative approach.
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