Analysis of time-to-event (“survival”) data typically requires two pieces of data that are taken into account simultaneously: i) the time period for which follow-up was available, and ii) the status at the end of the follow-up. The former variable is continuous (time) and the latter categorical, specifying whether the endpoint was the event under study, such as death or relapse had occurred, or if whether it had yet to occur when follow-up end. Follow-up times often varies between individuals in a study due to recruitment over time and also due to withdrawal from follow-up, loss-to-follow-up or the occurrence of another event (e.g. death from an unrelated cause), often referred to as a competing risk, which precludes the occurrence of the event of interest (e.g. recurrence of the disease of interest).