Analysis of survival outcomes in haematopoietic cell transplant studies: Pitfalls and solutions

Abstract

SERIES EDITOR INTRODUCTIONThe final article in our Statistics Series by de Wreede and colleagues deals with the important issue of survival analyses in general and in recipients of haematopoietic cell transplants specifically. At first glance analyzing survival should be simple. The endpoint is clear with rare exception, the subject is either alive or dead. Compare this to other less well defined transplant-related outcomes such as who has acute graft-versus-host disease (GvHD) and of what grade or what is the cause of interstitial pneumonia. There is also the complexity of composite endpoints when one analyzes outcomes such as event-free (EFS) or relapse-free survival (RFS).Here you're either alive or dead. Period. Alas, as it turns out things are not so simple. As the authours point out: it takes time to observe time. It is almost never possible to wait long enough for everyone in a study to die. (Some people who are cured by a transplant will outlive their physician and statistician.) Other subjects may not be followed until the end of the study, lost to followup or withdraw consent to participate. Often these are non-random events, muddy the water and make what seems a simple analysis of survival not so. Fortunately, de Wreede and colleagues discuss the issues of informative and non-informative censoring and time-dependent co-variates. And there are other nasty complexities such non-proportional hazards of death say when initially there is a survival disadvantage to transplants from transplant-related mortality followed in 1-2 years by a survival benefit. They emphasize the danger of considering only Hazard Ratio in this setting. Lastly, the authours discuss how to compare interventions such as conventional therapy versus a haematopoietic cell transplant when the endpoint of interest is survival. We think this article will be of considerable interest to readers of BONE MARROW TRANSPLANTATION and suggest you study it carefully. Survival analyses, seemingly simple, are a potential minefield. You don't want to step on one. This article and the entire Statistics Series are available online at https://www.nature.com/collections/ejhigdbeeh.

Colonization by multidrug‐resistant bacteria in hematological patients undergoing hematopoietic stem cell transplantation and clinical outcomes: A single‐center retrospective cohort study

“…All statistical analyses were performed in accordance with recommendations from the European Group for Blood and Marrow Transplantation 25,26 , and using the EZR software version 1.53 (Saitama Medical Center, Jichi Medical University).…”