title: Sample sizes in dosage investigational clinical trials: a systematic evaluation.
abstract: 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.
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Ji-Han
authors.initials: JH
authors.lastname: Huang
authors.affiliation: Department of Computer, College of Electronic and Electrical Engineering, Shanghai University of Engineering Science, Shanghai, People's Republic of China.
authors.forename: Qian-Min
authors.initials: QM
authors.lastname: Su
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Yang
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Ying-Hua
authors.initials: YH
authors.lastname: Lv
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: He
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Jun-Chao
authors.initials: JC
authors.lastname: Chen
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Ling
authors.initials: L
authors.lastname: Xu
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.affiliation: Center for Drug Clinical Research, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
authors.forename: Qing-Shan
authors.initials: QS
authors.lastname: Zheng
mesh_terms: D017322:Clinical Trials, Phase II as Topic / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D054796:Drug Dosage Calculations; D006801:Humans; D018401:Sample Size
keywords: dose-finding; dose-response; sample number; systematic review