DFS and OS by MRD response to imatinib treatment, determined by longitudinal analysis of bcr-abl transcript levels after study entry, at which all patients were PCR positive. Median DFS and OS in patients achieving early PCR negativity was significantly superior to that in patients who remained MRD⁺ after initiation of imatinib (28.6 months versus 3.6 months, P < .001; and median not yet reached versus 7.1 months, P < .001, respectively). The estimated DFS and OS rates in the MRD^– group were 54.5% ± 21% and 80% ± 18% at 24 months compared with 8% ± 7% and 23% ± 13% in the MRD⁺ group, respectively. The event at month 21 is due to a death in CR.