A treatment allocation procedure for sequential clinical trials.

A dynamic treatment allocation procedure is proposed for clinical trials which require balancing across several prognostic factors. The treatment allocation decision is based on the minimization of a function which is an easily evaluated approximation to the variance of the treatment effect in a linear model relating the outcome variable to the chosen prognostic factors and selected interactions. By use of simulations, the procedure is shown to be superior to ad hoc procedures proposed by Pocock and Simon (1975, Biometrics 31, 103-115), over a variety of reasonable experimental situations. It is shown that it is feasible to evaluate the procedure by hand calculations and that it is extremely easy if a small programmable calculator is available. Practical problems relating to implementation of the procedure are discussed with special reference to multi-institutional clinical trials.