UCL School of Management is delighted to welcome Prof. Steve Chick, INSEAD, to host a seminar discussing “A Bayesian Decision-Theoretic Model of Sequential Clinical Trials with Delayed Responses and Extensions”.
Clinical trials are necessary for evaluating the benefit of health technologies but are quite costly, and have therefore been the subject of much study. Delayed observations have been receiving increased attention in the clinical trial literature, but the effects of delayed observations have not been explored in depth, especially in the context of sequential trials and health technology assessments, where health value for money spent is increasingly seen as being important for driving technology choice decisions. We propose and solve a Bayesian decision-theoretic model of a fully sequential experiment in which the end point is observed with delay, and where the end point focuses on health economics rather than abstract statistical criteria. We identify sequential experiments which maximize the expected benefits of technology adoption decisions, minus sampling costs. The solution yields a unified policy defining the optimal `do not experiment’/`fixed sample size experiment’/`sequential experiment’ regions and optimal stopping boundaries for sequential sampling, as a function of the prior mean benefit and the size of the delay. The model can also value the expected benefits accruing to study units and the fixed costs of switching from control to treatment. We apply the model to the field of medical statistics, using data from a published trial investigating the clinical- and cost-effectiveness of drug-eluting stents versus bare metal stents. We show that it is important to properly account for delay in trial design, and comment on some current work in highly-sequential, highly-multiarm trial design.