In CML, the presence of the Ph+ chromosome and levels of BCR-ABL transcript can act as chromosomal and molecular markers of disease, respectively, and hematologic, cytogenetic, and molecular responses can thus be monitored in CML patients at defined time points according to principles proposed by European Leukemia Net (ELN) and the National Comprehensive Cancer Network (NCCN) 72, 73. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.