Sample size determination in group-sequential clinical trials with two co-primary endpoints

Koko Asakura, Toshimitsu Hamasaki, Tomoyuki Sugimoto, Kenichi Hayashi, Scott R. Evans, Takashi Sozu

Research output: Contribution to journalArticle

13 Citations (Scopus)


We discuss sample size determination in group-sequential designs with two endpoints as co-primary. We derive the power and sample size within two decision-making frameworks. One is to claim the test intervention's benefit relative to control when superiority is achieved for the two endpoints at the same interim timepoint of the trial. The other is when superiority is achieved for the two endpoints at any interim timepoint, not necessarily simultaneously. We evaluate the behaviors of sample size and power with varying design elements and provide a real example to illustrate the proposed sample size methods. In addition, we discuss sample size recalculation based on observed data and evaluate the impact on the power and Type I error rate.

Original languageEnglish
Pages (from-to)2897-2913
Number of pages17
JournalStatistics in Medicine
Issue number17
Publication statusPublished - 2014 Jul 30



  • Average sample number
  • Co-primary endpoints
  • Conditional power
  • Cui-Hung-Wang statistics
  • Group-sequential methods
  • Maximum sample size
  • Sample size recalculation
  • Type I error

ASJC Scopus subject areas

  • Epidemiology
  • Statistics and Probability

Cite this