BCR and chronic myelogenous leukemia, BCR-ABL1 positive: In addition, patients with CML who achieve optimal responses to first- or second-line TKI therapy (defined as sustained, deep remissions of greater than 4–5 log10 reductions in BCR–ABL transcript using the International Scale) may be candidates for drug cessation after multiple years of TKI therapy, showing us the capacity of MRD to guide therapy discontinuation [13].