Disease overview: Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100 000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults.
Diagnosis: CML is characterized by a balanced genetic translocation, t(9;22)(q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR-ABL1 fusion oncogene, which in turn translates into a BCR-ABL1 oncoprotein. Frontline therapy: Four tyrosine kinase inhibitors (TKIs), imatinib, nilotinib, dasatinib, and bosutinib are approved by the United States Food and Drug Administration for first-line treatment of patients with newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses; this has not translated into improved long-term survival, because of the availability of effective salvage therapies. Salvage therapy: For patients who fail frontline therapy, second-line options include second and third generation TKIs. Second and third generation TKIs, although potent and selective, exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR-ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP who have failed at least 2 TKIs, and for all patients in CML advanced phases.
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