Quality of life during clinical trials: conceptual model for the Lung Cancer Symptom Scale (LCSS).
To appreciate the full benefits of treatment for lung cancer, especially in trials that fail to show improvements in survival, data recording the quality of life must be captured and refined to produce meaningful information. A conceptual model for quality of life for lung cancer patients was tested to obtain information about the dimensions of the quality-of-life construct for ongoing development and testing of a subjective measure for clinical trials. Using a longitudinal study design, the stability of predictive factors of the physical and functional dimensions of quality of life were examined using regression analysis. A patient-rated quality-of-life measure, the Lung Cancer Symptom Scale (LCSS), was administered to 144 non-small-cell lung cancer patients at baseline, day 29, and day 71 of a chemotherapy trial. The range of explained variance for all three components of the lung cancer model over three assessment points was as follows: symptomatic distress 41%-53%, activity status 48%-52%, and overall quality of life 35%-53%. The three dimensions fluctuated slightly during intervention, but were relatively stable factors across all three times of evaluation. The LCSS model explained nearly half of the variance for quality of life experienced by lung cancer patients during therapy with a new chemotherapeutic agent. These findings provide support that the physical and functional dimensions are important predictors of quality of life for individuals with lung cancer. Meaningful subjective quality-of-life data can be obtained to evaluate an intervention by using a disease- and site-specific quality-of-life measure for individuals with lung cancer, based on a reproducible conceptual model such as the LCSS, which is suitable for serial measurement for the progressive disease of lung cancer.