Conditional power for arbitrary survival curves to decide whether to extend a clinical trial.
This article describes a computer simulation methodology to calculate conditional power for comparing two arbitrary survival curves as an aid in deciding whether or not to extend a clinical trial. The method is a modification of that by Halpern and Brown, which computes unconditional power for comparing arbitrary survival curves at the beginning of a study. The advantage of this method is that it permits conditional power calculations for comparisons of distribution-free survival curves. Power is computed for two commonly used statistical tests, the log-rank test and Gehan's generalization of the Wilcoxon test, and for a modified Kolmogorov-Smirnov test, which is particularly sensitive to crossing survival curves. This method for estimating conditional power should be useful in the situation in which a decision must be made regarding the benefit of continuing a clinical trial. The application of this method is shown using VA Cooperative Study No. 90, "Prognosis and Outcome Following Heart Valve Replacement."
Henderson
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WG
VA Cooperative Studies Program Coordinating Center, VA Hospital, Hines, IL 60141.
Fisher
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SG
Weber
L
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Hammermeister
K E
KE
Sethi
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G
D001021:Aortic Valve / Q000601:surgery; D002986:Clinical Trials as Topic / Q000379:methods*; D003198:Computer Simulation; D005500:Follow-Up Studies; D006349:Heart Valve Diseases / Q000601:surgery; D006350:Heart Valve Prosthesis / Q000401:mortality; D006801:Humans; D008432:Mathematical Computing; D008943:Mitral Valve / Q000601:surgery; D011475:Prosthesis Failure; D011897:Random Allocation; D016019:Survival Analysis