What Is CML Blast Crisis?
Chronic myeloid leukemia (CML) in blastic phase is the transition of CML in chronic or accelerated phase to an acute leukemia, characterized by 30% blasts in the bone marrow or peripheral blood, or the development of extramedullary disease outside of the spleen. In light of recent changes in the World Health Organization definition of acute leukemia, the percentage of blasts required for CML in blastic phase may someday be reduced to 20%. Consistent with the early stem cell nature of CML,1 blastic transformation may be myeloid, lymphoid, or undifferentiated/mixed, with myeloid blast crisis being about two times more common than lymphoid. Although the definition of CML in blastic phase has not changed from the pre- to post-imatinib era, the treatment history of our current CML patient population has: an ever-increasing proportion of patients with CML will have been managed exclusively with imatinib or other ABL kinase inhibitor therapy. Such a significant change in therapeutic approach
