Quality-adjusted survival analysis of malignant glioma patients

The goal of therapeutic intervention in oncology patients is to prolong survival without compromising its quality. Definition and measurement of quality are quite difficult. This article discusses the statistical techniques for quantifying quality survival that have been used in brain tumor patients. These techniques assume either that all patients have equivalent baseline quality of life when both disease-related symptoms and toxicities are absent, or that the length of time with a predetermined level of impairment is equivalent to death. These models do not fit the heterogeneous symptoms experienced by patients with malignant brain tumors. We propose a model that incorporates the baseline states with transitions to different levels of severity that indicate improvement and/or declines in physical and cognitive functioning of brain tumor patients. The length of time spent in each state is observed and weighted by using predetermined utilities. The weighted time spent in each state is aggregated over all states into a quality-time of survival metric (QTIME). This QTIME model was applied to a previously published, randomized clinical trial of different radiation doses in malignant brain tumor patients.