The **data** were divided into 8 strata based on institutional histology, relapse and study with strata sizes (1257,1769,107,113,223,284,84,78). In the simulation study, 720 individuals were sampled at phase 2. Based on above outcome model and the whole cohort data, the optimal phase-2 sample sizes for each stratum were n opt = (156,241,38,39,75,111,36,24).