ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Against this background, we aimed to investigate whether serial monitoring of BCR-ABL by RT-qPCR, but not cytogenetic analysis, to measure minimal residual disease (MRD), performed throughout imatinib treatment in CP-CML patients having achieved CCyR and MMR, could be safely used to monitor patients and predict the probability of relapse within a clinically relevant time period and to guide therapy.