Interim recruitment goals in clinical trials.

The recruitment rate or duration of a clinical trial must be so determined that the required number of patients may be assured within the given design frame. Establishing interim recruitment goals in clinical trials will not only help keep the clinical investigator from falling too far behind in recruitment but will also enable the sponsor of the study to decide in the early stages of the study whether the investigator can achieve the final recruitment goal. We propose statistical methods for determining a proper recruitment rate, duration and interim recruitment goals. A method of projecting the final recruitment at interims and a method of adjusting the recruitment duration at interims are discussed. Seasonal adjustment methods are also noted.