Sample sizes in dosage investigational clinical trials: a systematic evaluation

Abstract

Ji-Han Huang,1,* Qian-Min Su,2,* Juan Yang,1 Ying-Hua Lv,1 Ying-Chun He,1 Jun-Chao Chen,1 Ling Xu,1 Kun Wang,1 Qing-Shan Zheng11Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People’s Republic of China; 2Department of Computer, College of Electronic and Electrical Engineering, Shanghai University of Engineering Science, Shanghai, People’s Republic of China *These authors contributed equally to this workAbstract: The main purpose of investigational phase II clinical trials is to explore indications and effective doses. However, as yet, there is no clear rule and no related published literature about the precise suitable sample sizes to be used in phase II clinical trials. To explore this, we searched for clinical trials in the ClinicalTrials.gov registry using the keywords “dose-finding” or “dose–response” and “Phase II”. The time span of the search was September 20, 1999, to December 31, 2013. A total of 2103 clinical trials were finally included in our review. Regarding sample sizes, 1,156 clinical trials had <40 participants in each group, accounting for 55.0% of the studies reviewed, and only 17.2% of the studies reviewed had >100 patient cases in a single group. Sample sizes used in parallel study designs tended to be larger than those of crossover designs (median sample size 151 and 37, respectively). In conclusion, in the earlier phases of drug research and development, there are a variety of designs for dosage investigational studies. The sample size of each trial should be comprehensively considered and selected according to the study design and purpose.Keywords: sample number, dose-finding, dose–response, systematic review