Two BCR-ABL1 measurements may be insufficient to assess the trend of decline in some patients. (A) At 3 months of imatinib, BCR-ABL1 had declined and the trend suggested the value may decline out of the failure zone at 6 months. (B-C) After an initial reduction at 1 month, BCR-ABL1 reached a plateau and the patient clearly failed therapy at 3 and 6 months. A kinase domain mutation was not detected at 1 month and the patient possibly acquired a BCR-ABL1–independent resistance mechanism.