Clinical trials : journal of the Society for Clinical Trials
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In an ongoing multi-center randomized control clinical trial, the Carotid Occlusion Surgery Study (COSS), the study protocol specifies multiple interim analyses whose results will be reviewed by an independent DSMB to determine if the trial needs to be stopped early due to either efficacy or futility. Conditional power is used as the decision rule for the DSMB to recommend stopping the trial for futility. An aggressive rule for futility stopping sets a relatively high threshold for the conditional power which may result in significant loss of overall power of the study. A conservative rule using a lower threshold may not be able to stop the trial early when there is indeed no treatment efficacy. ⋯ The proposed conditional power method facilitates a flexible futility monitoring plan that can be easily implemented in long-term clinical trials where multiple interim analyses are required. It provides the DSMB an objective guideline to use in considering early stopping for futility. Clinical Trials 2010; 7: 209. http:// ctj.sagepub.com.