Quality of life assessment for cost/utility studies in cancer

The goals of cancer treatment and cancer prevention are to extend life expectancy and to improve quality of life in the years prior to death. Typically, outcomes of cancer treatment are evaluated in terms of survival time. Although quality of life is often measured, interpretation of these outcomes in relation to mortality is difficult. Survival analysis places each individual into one of two categories: alive or dead. Among those alive, all individuals are considered equivalent. Thus, a patient confined to bed with severe symptoms is scored the same as someone who is active and asymptomatic. A General Health Policy Model is proposed as a solution to this problem. The model adjusts life expectancy for diminished quality of life, which is measured using a standardized instrument known as the Quality of Well-being (QWB) scale. The model expresses the effect of treatment in a unit known as a Well-Year or Quality Adjusted Life Year (QALY). These units integrate side-effects and benefits of treatment by combining into a single number, mortality, morbidity, and duration of each health state. Similar methods, such as the Q-TWiST, have been proposed for use in cancer clinical trials. However, the Q-TWiST is a subset of the more general model and carries limitations for cross-disease comparisons. We conclude that general health outcome models can be of considerable value for analysing the costs, risks and benefits of cancer therapies.