Quality of life: what is it? How should it be measured?

Efforts have recently been mounted to introduce subjective or "quality of life" parameters as an integral part of the evaluation process in clinical cancer research. While there is no universally accepted definition of the quality of life concept, in oncology it is most often used to describe such aspects of health status as physical symptoms, daily activity level, psychological well-being, and social functioning. The major challenge is to develop measures of the various dimensions of quality of life that, while meeting rigorous standards of validity and reliability, also reflect an appreciation of the practical constraints typically operating in clinical research settings. This overview highlights some of the basic issues surrounding quality of life measurement in oncology.