Quality of life assessment in cancer clinical research: current status and a look to the future.

Quality of life (QOL) is a term that has been used to denote outcomes as experienced by the patient. Although definitions of QOL vary, virtually all investigators agree that QOL in clinically-ill individuals encompasses multiple domains or areas of well-being (including, at a minimum, physical, psychological and social functioning, as well as symptoms) and that the perspective of the patient is critical in any measurement of QOL. While patient perspectives are important in any health condition, they become particularly so in diseases which are chronic or incurable and for which treatments have toxic or long-lasting consequences. Cancer fits these criteria. Cancer is the second leading cause of death in the USA, with one in every four deaths due to the disease. Approximately 38% of cancer patients die within 5 years of diagnosis. Cancer treatments are powerful and toxic. For example, surgery removes tumors and in many cases, adjacent body parts. Radiation therapy kills cancer cells by directing high energy x-rays, electron beams or radioactive isotopes at tumors. Chemotherapy causes the death of cancer cells through the administration of agents that disrupt a cancer cell's growth cycle. All of these treatments affect normal tissue, as well as cancer cells, and generally result in multiple side effects, such as loss of hair, nausea and frequently vomiting which are associated with chemotherapy. Treatment-related effects may be short-term and time-limited, chronic and persistent or late that only emerge after therapy has been completed, sometimes many years later. Cancer therapy involves continual efforts to minimize side effects while at the same increasing the chances of surviving the disease. As such, patient perspectives become critical in evaluating whether or not therapies and their toxicities are tolerable and acceptable.