Essence of survival analysis†

Abstract

Many clinical trials are designed based on a time-to-event endpoint. Overall survival and progression-free survival are commonly used, especially in Phase II and III clinical trials. Overall survival measures the time to death from any cause, while progression-free survival measures the time to progression of the disease or death from any cause. The key distinguishing factor is that the event of interest, such as death, may not occur in all individuals, making their time to this event unknown. Survival analysis comprises of the methods used to estimate the rates associated with time-to-an-event data, compare the rates between groups, and assess how other factors impact these rates.