ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: However, the persistence of BCR/ABL transcripts in a cohort of patients with complete cytogenetic response (Hughes et al, 2003) and the resistance of the primitive CML stem cell to imatinib treatment (Copland et al, 2006) raises the possibility that treatment with imatinib alone might delay but not prevent disease progression.