Safety and Effectiveness of the SVELTE Fixed-Wire and Rapid Exchange Bioresorbable-Polymer Sirolimus-Eluting Coronary Stent Systems for the Treatment of Atherosclerotic Lesions: Results of the OPTIMIZE Randomized Study

Consequences of Inaccurate Assumptions in Coronary Stent Noninferiority Trials: A Systematic Review and Meta-analysis

IMPORTANCE

The outcome and interpretation of noninferiority trials depend on the magnitude of the noninferiority margin and whether a relative or absolute noninferiority margin is used and may be affected by imprecision in event rate estimation.

OBJECTIVE

To assess the consequence of imprecise event rate estimations on interpretation of peer-reviewed randomized clinical trials.

DATA SOURCES

PubMed/MEDLINE was searched for articles published between January 1, 2015, and April 30, 2021.

STUDY SELECTION

Noninferiority randomized clinical trials of coronary stents published in selected journals with clinical events as the primary end point.

DATA EXTRACTION AND SYNTHESIS

Two reviewers (M.S. and F.V.) independently extracted data on trial characteristics, noninferiority assumptions, primary end point clinical outcomes, and study conclusions. Overestimation or underestimation of the control event rate was evaluated by dividing the assumed control event rate by the observed control event rate. For noninferiority end points with absolute margins, the assumed corresponding relative margin was defined as the ratio of the absolute margin and the assumed event rate, and the observed corresponding relative margin as the ratio between the absolute margin and the observed event rate in the control arm. Noninferiority comparisons with absolute margins were reanalyzed using the assumed corresponding relative margin and the Farrington-Manning score test for relative risk.

MAIN OUTCOMES AND MEASURES

Overestimation or underestimation, assumed and observed corresponding relative margins, and relative reanalysis of the primary end points of trials with absolute margins.

RESULTS

A total of 106 989 patients from 58 trials were included. The event rate in the control arms was overestimated by a median (IQR) of 28% (2%-74%). Most noninferiority trials used absolute rather than relative margins (55 of 58 trials [94.8%]). Owing to overestimation, absolute noninferiority margins became more permissive than originally assumed (median [IQR] of observed relative noninferiority margin, 1.62 [1.50-1.80] vs assumed relative noninferiority margin, 1.47 [1.39-1.55]; P < .001). Among trial comparisons that met noninferiority with an absolute noninferiority margin, 17 of 50 trials (34.0%) would not have met noninferiority with a corresponding assumed relative noninferiority margin.

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, assumed event rates were often overestimated in noninferiority coronary stent trials. Because most of these trials use absolute margins to define noninferiority, such overestimation results in excessively permissive relative noninferiority margins.

Understanding the Merits and Drawbacks of Noninferiority Trials in Cardiovascular Medicine

A noninferiority trial is designed to show that the new treatment is not unacceptably worse than the standard treatment by more than a predefined noninferiority margin. These trials are typically performed when standard placebo-controlled trials are considered to be unethical or impractical and the new treatment offers advantages over the existing standard treatment in terms of safety, convenience, or cost. Given that noninferiority trials are being performed with increasing frequency in cardiovascular applications, it is important to understand their complex trial design and analysis. This narrative review aims to provide readers with a detailed perspective on the goals, characteristics, design, and analysis of noninferiority trials. Trials designed to show noninferiority require an appropriate reference population, a proven standard treatment and dose, an appropriate margin of noninferiority that is statistically justifiable (based on historical placebo-controlled trials evaluating standard treatment effect) and clinically reasonable (choosing the fraction of the effect of the standard drug that should be "preserved" by the new drug), a high level of adherence to treatment, and adequate statistical power to reliably conclude that a treatment is truly noninferior and therefore effective. The merits and pitfalls of noninferiority trials, with representative contemporary cardiovascular clinical trials in interventional cardiology, cardiac surgery, and atrial fibrillation management as exemplars, are described. The key issues that challenge the design, conduct, analysis, interpretation, and implementation of these trials are discussed, and a variety of ways to identify and mitigate key errors are recommended to allow for optimal evaluation of noninferiority trials conducted in cardiovascular medicine.