Clustering by gene-expression profiling and principal component analysis of 286 diagnostic samples of childhood ALL in relation to risk of relapse. Signals represent the 15 probe sets (14 genes) that were associated with MRD on day 19, and independently predicted outcome. (A,B) Heat map and principal component analysis. Clusters are indicated in blue and red. (C) Cumulative incidence of relapse among the 99 patients enrolled on Total XIII belonging to each cluster (P < .001).