Power calculation for clinical trials when the outcome is a composite ranking of survival and a nonfatal outcome.

In a clinical trial in which mortality occurs and a nonfatal outcome is measured after a fixed duration of follow-up, composite rank scores in which deaths (ranked by survival time) are scored below ranks for the nonfatal outcome have been proposed to test for treatment efficacy. This report derives formulae for calculating power for such a rank test under the conservative assumption that the treatment has a beneficial effect on the nonfatal outcome but no effect on mortality.