A scheme for a dose-escalation study when the event is lagged

Classical designs for clinical phase I trials assume that information about a dose-limiting event (DLE) is available for all the included patients, or advise not to treat new patients until the information is present. If a DL E occurs after a lag, however, information at the current time might not be sufficient to make clear-cut decisions according to these designs. In part icular, if new patients are available, it is not clear whether to include t hem in the trial. We suggest a rule that decides on the accrual of each ind ividual eligible patient. Simulation studies are presented that indicate an advantage over the standard 'three-at-once' design in the length of the st udy. Copyright (C) 2001 John Wiley & Sons, Ltd.