Trial-related quality of life: using quality-of-life assessment to distinguish among cancer therapies.

Issues in selecting quality-of-life (QOL) measures that are best suited to assessing differences among treatments in cancer clinical trials, as well as challenges to interpreting QOL outcome data, are discussed. When used in the context of randomized trials of cancer therapies, QOL assessments must provide an answer to the question, "Did the treatments differentially affect patient well-being?" In order to detect differences in treatment efficacy against a background of great similarity, the broad concept of QOL needs to be refined to reflect "trial-related QOL." In many cases, this will entail emphasis on actual patient experience of symptoms and functional changes, as opposed to emphasis solely on evaluation and satisfaction. A model is proposed to identify cognitive, emotional, and sociocultural factors that influence a patient's QOL evaluation and that need to be considered in understanding the meaning of QOL data.