[Significance and problems of quality-of-life assessment in clinical trials]

The importance of quality of life (QOL), as an outcome variable of cancer treatments, has rapidly become recognized not only in western countries but also in Japan. However, many problems remain to be resolved for QOL assessment methods. In this paper, we give outlines for the position of QOL as an outcome variable, the standpoint and purpose for QOL assessment, the appropriate range of QOL domains to be assessed, and the appropriate QOL measures. Furthermore, we introduce key points for the success of QOL assessment in clinical trials, the appropriate way to deal with missing data and appropriate methods for analysis in longitudinal studies.