Quality of life in cancer patients--an hypothesis.

Quality of life is a difficult concept to define and to measure. An hypothesis is proposed which suggests that the quality of life measures the difference, or the gap, at a particular period of time between the hopes and expectations of the individual and that individual's present experiences. Quality of life can only be described by the individual, and must take into account many aspects of life. The approach is goal-orientated, and one of task analysis. The hypothesis is developed in a diagramatic way, and several methods of testing the hypothesis suggested.