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Table 1 Design parameters by trial stage for original research arms

From: Flexible trial design in practice - stopping arms for lack-of-benefit and adding research arms mid-trial in STAMPEDE: a multi-arm multi-stage randomized controlled trial

Trial Stage Type Primary outcome measure Target hazard ratio Power One-sided Significance level Critical HR Trigger events1(control)
1 Activity FFS 0.75 95% 0.500 1.00 114
2 Activity FFS 0.75 95% 0.250 0.92 215
3 Activity FFS 0.75 95% 0.100 0.89 334
4 Efficacy OS 0.75 90% 0.025 - 400
Overall - - - 83% 0.013 - -
  1. 1 Number of control arm events provoking analyses for the original research comparisons with a 2:1 allocation ratio in favour of control. The required number of events would be different for an equal allocation ratio.
  2. Key: FFS = failure-free survival; OS = overall survival; HR = hazard ratio.
  3. Note: these parameters are used for each pairwise comparison of research vs control.