Fig. 1
From: Designs for adding a treatment arm to an ongoing clinical trial
Example of adding a single experimental treatment arm to a two-arm trial comparing treatment 1 to control. The first dashed vertical line represents when the new treatment arm (treatment 2) is added to the trial. The second dashed vertical line represents when the original treatment (treatment 1) finishes recruitment and the third dashed vertical line represents when the control and treatment 2 finish recruiting patients. The horizontal dashed lines represent the additional patients required per treatment group above the original sample size estimate to control the FWER whilst maintaining randomisation of 1:1:1 to all treatment arms