Unprecedented Megakaryocytic Blast Phase Transformation in Chronic Myeloid Leukemia After 16 Years of Tyrosine Kinase Inhibitor Therapy.

We report the case of a 51-year-old Japanese man with chronic myeloid leukemia (CML) initially diagnosed in the chronic phase. For 16 years, the patient maintained chronic phase (CP) under treatment with first- and second-generation tyrosine kinase inhibitors (TKIs), including imatinib, dasatinib, and bosutinib, none of which resulted in ABL1 mutations. However, despite long-term disease stability, the patient experienced an abrupt progression to the megakaryocytic blast phase (MBP), a rare and aggressive form of CML. In response to this progression, ponatinib, a third-generation TKI, was introduced as a fourth-line therapy. Remarkably, within 7 months of initiating ponatinib, the patient achieved a deep molecular response (DMR), evidenced by a reduction in BCR::ABL1 transcript levels to undetectable levels (MR ^5.0 ). This molecular remission enabled the patient to proceed with an allogeneic bone marrow transplantation from a human leukocyte antigen (HLA) 8/8-allele-matched unrelated donor. Post-transplantation, the patient has maintained DMR for 14 months without recurrence, despite the challenges posed by graft-versus-host disease. This case illustrates the critical role of third-generation TKIs like ponatinib in managing advanced CML phases, especially when previous therapies fail. It also emphasizes the necessity of vigilant long-term monitoring during the chronic phase to detect and address any signs of disease progression promptly.
Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.
(Copyright © 2024, Takatsuna et al.)