SAMPLE SIZES FOR RANDOMIZED TRIALS MEASURING QUALITY-OF-LIFE IN CANCER-PATIENTS

This paper describes the methods appropriate for calculating sample si zes for clinical trials assessing quality of life (QOL). An example fr om a randomized trial of patients with small cell lung cancer completi ng the Hospital Anxiety and Depression Scale (HADS) is used for illust ration. Sample size estimates calculated assuming that the data are ei ther of the Normal form or binary are compared to estimates derived us ing an ordered categorical approach. In our example, since the data ar e very skewed, the Normal and binary approaches are shown to be unsati sfactory: binary methods may lead to substantial over estimates of sam ple size and Normal methods take no account of the asymmetric nature o f the distribution. When summarizing normative data for QOL scores the frequency distributions should always be given so that one can assess if non-parametric methods should be used for sample size calculations and analysis. Further work is needed to discover what changes in QOL scores represent clinical importance for health technology interventio ns.