blast phase
Advanced stage of chronic myeloid leukemia characterized by ≥20% blasts in blood or bone marrow, indicating transformation to acute leukemia.
Full Definition
Blast phase, also known as blast crisis, represents the terminal phase of chronic myeloid leukemia (CML) where the disease transforms from a chronic condition to an acute leukemia-like state. This phase is defined by the presence of 20% or more blast cells in the peripheral blood or bone marrow. In pediatric patients with CML, blast phase typically occurs within the first few years if untreated, though modern tyrosine kinase inhibitor therapy has dramatically reduced its incidence. The blast phase can be either myeloid or lymphoid in nature and carries a poor prognosis, often requiring intensive acute leukemia-type chemotherapy and consideration for stem cell transplantation.
Usage
Usage note: Use 'phase' rather than 'crisis' in current pediatric oncology practice.
In Context
- "The patient's CML progressed to blast phase despite initial response to imatinib therapy." — Oncology progress note
- "Flow cytometry confirmed lymphoid blast phase, requiring ALL-directed chemotherapy protocols." — Pathology consultation