Comparing Time-t o-Event Data
In clinical research, in addition to continuous and discrete study endpoints described in the previous two chapters, the investigator may also be interested in the occurrence of certain events such as adverse experience, disease progression, relapse, or death. In most clinical trials, the occurrence of such an event is usually undesirable. Hence, one of the primary objectives of the intended clinical trials may be to evaluate the effect of the test drug on the prevention or delay of such events. The time to the occurrence of an event is usually referred to as the time-to-event. In practice, time-to-event has become a natural measure of the extent to which the event occurrence is delayed. When the event is the death, the time-to-event of a patient is the patient's survival time. Hence, the analysis of time-to-event is sometimes referred to as survival analysis.