Planning clinical trials to evaluate early detection programmes

SUMMARY The lack of statistical theory for the planning of early detection trials has resulted in current trials being sub-optimal. We develop probability models that address three characteristics of early detection trials: (i) the optimal time of analysis and length of follow-up, (ii) the optimal spacing between examinations, and (iii) the planning of trials where the numbers of examinations versus sample size are balanced for fixed costs. The optimisation criterion is to maximise the power of the statistical test for comparing mortality. Application is made to breast cancer early detection trials.