Designing Phase II Studies in the Context of a Programme of Clinical Research

Conventional statistical determinations of sample size in phase II studies typically lead to sample sizes of the order of 25 (Schoenfeld, 1980, International Journal of Radiation Oncology, Biology and Physics 6, 371-374). When the development of new treatments is proceeding rapidly relative to the recruitment of suitable patients, such requirements can prove to be too demanding. As a result, either sample sizes are reduced by a rather arbitrary weakening of the risk specifications, or certain new treatments go untested. In this paper, the phase II testing of a number of treatments will be considered as a single study which has the objective of identifying the most promising treatment for phase III investigation. It is seen to be advantageous to test more treatments, with fewer subjects receiving each, than the conventional methods would allow.