TABLE 1.

Timing of interim analyses and posterior probabilities required to stop for success (S) or futility (F) at each interim analysis, and final analysis success criteria for the case study

Interim analysis	Number of patients with complete follow‐up	$S_i$	$F_i$
1 a	500	NA	NA
2	750	0.9984	0.1003
3	1000	0.9963	0.2591
4	1250	0.9928	0.5411
Final b	Max 1500	0.9875	NA

Note: $S_i$ is the stopping boundary for superiority at the i‐th analysis; $F_i$ is the stopping boundary for futility at the i‐th analysis.

^a Only response adaptive randomization (RAR) was performed at the first interim analysis (i.e., no early stopping for efficacy or futility was permitted).

^b If the trial did not stop early for efficacy or futility, the final analysis was performed once 1500 patients were recruited and followed up; if the trial stopped early, then the final analysis was performed once the recruited patients completed follow‐up.