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Abstract:
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For studies with 2 x 2 factorial designs, the complexity of determining an appropriate futility analysis plan is increased as compared to studies where patients are randomized to one treatment. Issues that must be addressed include the possibility of a significant interaction and the need to determine how to proceed given evidence of futility in one arm. Suggested approaches include a two-stage plan, which first assesses futility of the interaction term and proceeds to examine the main effects given sufficient evidence that no interaction is present, and variations on one-stage plans, which assume the trial will not be stopped for futility in the interaction. We will summarize issues inherent to monitoring futility in 2 x 2 factorial studies, compare statistical properties of various approaches, and make recommendations as to which approach is preferred.
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