Simultaneous analysis of quality of life and survival data

In many phase III clinical trials, particularly in the field of cancer, the comparison of treatments is based on both length of survival and quality of life. Subjects are followed over time until death and during this period, quality of life is assessed on a number of occasions. Simultaneous analysis of these two outcomes supplements the comparison of treatments in terms of each outcome independently with an assessment of the net effect. In addition, it provides a means of accounting for the informative dropout due to death of patients within the time frame of the quality of life study. The methods also have the potential to be extended to allow for informative dropout from the quality of life study prior to death. There are a number of broad approaches for the simultaneous analysis of quality of life and survival data. The most widely used approach in clinical research is quality-adjusted survival analysis, where treatments are compared in terms of a composite measure of quality and quantity of life. The paper reviews the different techniques for quality-adjusted survival analysis, illustrating the methodology by application to data from a phase III clinical trial in pancreatic cancer. In addition, alternative approaches using multistate survival analysis and joint modelling methods are also discussed.