[Lymphoid blast crisis in chronic myeloid leukemia after long-term treatment-free remission following imatinib treatment].

A 55-year-old man started imatinib at 400 mg/day in 2002 for chronic myeloid leukemia in chronic phase (CML-CP). He maintained a complete cytogenetic response and achieved undetectable BCR::ABL1 mRNA levels by 2015, indicating a deep molecular response (DMR). He discontinued tyrosine kinase inhibitor (TKI) therapy in 2018 after maintaining DMR for over two years, but lost DMR in December 2022. Nine months later, BCR::ABL1 mRNA was detected at 0.08% IS. Although we recommended resuming TKI therapy, the patient declined. Within two months, a blood test revealed a lymphoblast ratio of 56.7%, leading to a diagnosis of lymphoid blast crisis. The patient achieved complete hematological remission after one cycle of dasatinib combined with hyper-CVAD/MA. Measurable residual disease persisted, and he underwent two cycles of inotuzumab ozogamicin therapy followed by allogeneic hematopoietic stem cell transplantation. This case highlights the critical need for vigilant follow-up in CML patients after prolonged TFR, given the risk of progression to blast crisis.