Quality of life: concepts and definition.

After years of second-class status, supportive care is increasingly being recognized for its importance. Included in this recognition is a concern for making more explicit the long-held conviction within medicine that no goal can logically be more important than optimal patient functioning and well-being. This effort to make more explicit the timeless value of medical care has evolved over the past two decades, and come to be labeled "quality of life" research. At its most fundamental level, quality of life is understood to be both subjective and multidimensional. Because it is subjective, it is best measured from the patient's perspective. Because it is multidimensional, its measurement requires the investigator to inquire about a range of areas of the patient's life, including physical well-being, functional ability, emotional well-being, and social well-being. The usual concern for symptom control, familiar to the palliative-care physician, can conceptually be expanded into a consideration of costs and benefits of various treatment options relative to their subjective perception of personal function and well-being. As our interest turns to the aggressive alleviation of specific ("target") symptoms, we must critically evaluate the complex relationships among symptom intensity, symptom duration, and overall quality of life.