Relation between MRD during and at the end of remission induction therapy with presenting features. Shown is the percentage of MRD on week 2 and week 6 of treatment according to presenting features in a cohort of 989 patients with newly diagnosed childhood ALL enrolled in St Jude Children's Research Hospital Total XIII-XV studies. Asterisks indicate P < .01 by chi square or Fisher's exact test; for genetic and biologic features, analyses were performed by comparing data from cases with a given feature to those of all other B-lineage cases, or T-lineage for early T-cell precursor ALL (ETP-ALL). Note that among the 23 BCR-ABL1 ALL patients studied on week 6, there were seven who were MRD^– and these included four of the five patients who received imatinib after day 19 of remission induction therapy. In the remaining patient who received imatinib-containing therapy, MRD went from 18.5% on week 2 to 0.06% on week 6.