on October 13, 2005
Published online before print October 13, 2005, doi: 10.1161/01.STR.0000185718.26377.07
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Submitted on February 9, 2005
From the Department of Biostatistics, Bioinformatics & Epidemiology (Y.Y.P., B.C.T., R.W.), Medical University of South Carolina, Charleston, SC; Trout Centre at Irish Lake (D.L.S.), Canada; and the Department of Neurology and Health Evaluation Sciences (K.C.J.), University of Virginia. * To whom correspondence should be addressed. E-mail: paleschy{at}musc.edu.
Background and Purpose--Most large, randomized phase III efficacy trials of therapeutic agents in ischemic stroke have failed to find treatment benefit. We determined whether some phase III studies could have been avoided if preceded by smaller single-arm phase II studies to evaluate the futility of proceeding to phase III. Methods--To provide examples of the application of phase II methodology, we obtained primary outcome data for the active treatment group of 6 phase III ischemic stroke therapy trials. For each study, we estimated the sample size number required for a multistage single-arm study using parameters specified in the original study. We evaluated outcome data for the first number of subjects in the phase III study treatment arm ordered by enrollment dates. We compared the proportion of favorable outcomes to prespecified stopping criteria derived from a single-arm phase II futility design. If the observed proportion of favorable outcomes was less than the stopping criterion, we declared the treatment not sufficiently effective to warrant further evaluation in phase III. Results--We identified 3 trials as futile in phase II; none of 3 showed treatment efficacy in phase III. In the 3 remaining phase II trials in which we did not show futility, one showed efficacy in phase III. Conclusion--Single-arm phase II futility studies have been underused in stroke research, but provide a strategy for discarding treatments likely to be ineffective in phase III trials.
Revised on May 2, 2005
Accepted on May 12, 2005
Applying a Phase II Futility Study Design to Therapeutic Stroke Trials
Yuko Y. Palesch PhD*;
Key words: clinical trials, phase II • ischemia • stroke
Related Article:
Stroke 2005 36: 2331-2332.
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