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The Philadelphia chromosome—or t(9;22)(q34.1;q11.2) resulting in a BCR-ABL1 fusion gene—is the hallmark of 90% to 95% of chronic myeloid leukemia (CML) cases. The remaining cases consist of variant and cryptic translocations that also result in the characteristic BCR-ABL1 fusion gene.
Spleen size (below costal margin) on examination
Complete blood count (CBC) with differential
Qualitative reverse transcription polymerase chain reaction (RT-PCR) for BCR-ABL
Bone marrow aspirate (BMA) and biopsy for morphology, karyotyping, and fluorescent in situ hybridization (FISH)
The three phases are chronic phase (CP), accelerated phase (AP), and blast phase (BP). There is no universally agreed on definition for AP- or BP-CML. The recommendation by the Children’s Oncology Group (COG) is to follow the classification by the World Health Organization (WHO; Table 32.1 ).
Chronic phase: Presence of all of the following criteria | Accelerated Phase: Presence of any of the following criteria | Blast Phase: presence of any of the following criteria |
---|---|---|
Less than 10% blasts in peripheral blood or bone marrow | 10%–19% blasts in peripheral blood or bone marrow | ≥20% blasts in peripheral blood or bone marrow |
Does not meet definition for accelerated or blast phase | Persistent or increasing WBC (> 10 × 10 9 ) unresponsive to therapy | Extramedullary blast proliferation |
Persistent thrombocytosis (>1000 × 10 9 ) unresponsive to therapy or persistent thrombocytopenia (<100 × 10 9 ) unrelated to therapy | ||
Blood basophils ≥20% in peripheral blood | ||
Persistent or increasing splenomegaly, unresponsive to therapy | ||
Additional clonal chromosomal abnormalities in Ph + cells at diagnosis, including major route abnormalities (second Ph chromosome, trisomy 8, isochromosome 17q, trisomy 19), complex karyotype, and abnormalities of 3q26.2 | ||
Any new clonal chromosomal abnormality in Ph + cells that occurs during therapy | ||
Provisional response criteria to TKI: Failure to achieve complete hematological response to first TKI; any hematological, cytogenetic, or molecular indications of resistance to two sequential TKI treatments; or occurrence of two or more mutations in BCR-ABL fusion gene during TKI therapy |
Stem cell transplant (SCT) was the only curative therapy for CML before tyrosine kinase inhibitors (TKIs) were introduced. Nevertheless, with the expansion of Food and Drug Administration (FDA)–approved TKIs for childhood CML, and their relatively safe profile compared with the potential risks and long-term toxicities of SCT, TKIs have replaced SCT as the primary treatment. There is no clear criteria for SCT, but it can be considered for the following conditions: BP or AP (either at diagnosis or as a progression from CP), failure of multiple TKIs, or significant toxicity from TKIs.
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