Chronic Myeloid Leukemia: Test and Diagnosis

1st order laboratory parameters – obligatory laboratory tests.

  • Small blood count [continuous left shift; leukocytosis/increase in white blood cells (leukocytes), erythrocytosis/increase in red blood cells (erythrocytes), thrombocytosis/increase in platelets (thrombocytes)]
  • Differential blood count [leukocytosis with basophilia]
  • Coagulation parameters – Quick, PTT (partial thromboplastin time).
  • Inflammatory parameters – CRP (C-reactive protein).
  • Alkaline leukocyte phosphatase (ALP; leukocyte AP) [ALP index: decreased].
  • Uric acid [↑]
  • LDH [↑]
  • Multiplex PCR (polymerase chain reaction) for BCR-ABL transcripts from peripheral blood – to confirm the diagnosis and as a starting point for therapy progression controlsNote: BCR-ABL is responsible for the oncogenic transformation of the affected hematopoietic stem cell.
  • Thymidine kinase (TK).
  • Cytology with blood smear
  • Bone marrow smear – for confirmation of diagnosis as well as confirmation of chronic phase of the disease and cytogenetic findings (Philadelphia chromosome (obsolete Ph1), additional aberrations if necessary).
    • Cytology (proportion of blasts and promyelocytes and distribution, eosinophils, basophils).
    • Cytogenetics: metaphase analysis
  • Bone marrow biopsy [cellularity, fibrosis, blast count and distribution].
  • CSF punctate
  • Cytogenetic testing and molecular genetics (Philadelphia chromosome (>95% of patients); BCR-ABL translocation) – for early identification of patients with suboptimal response and of relapses (regular follow-up to assess remission status).

Transaminases (alanine aminotransferase ALT, GPT); aspartate aminotransferase (AST; GOT)), electrolytes (sodium, potassium), and renal function parameters (urea, creatinine clearance) should be assessed before starting therapy. Criteria for the accelerated phase are:

  • 10-19% blasts in blood or bone marrow; or
  • > 20 % basophils in blood or bone marrow or
  • Therapy-independent thrombocytopenia (reduction in platelets) < 100,000/μl, not responding to therapy, or
  • Additional “major route” clonal chromosomal aberrations of Philadelphia-positive cells (second Philadelphia chromosome, trisomy 8, isochromosome 17q, trisomy 19, complex karyotype, aberrations of chromosomal segment 3q26.2) or
  • Newly formed clonal evolution or
  • Progressive splenomegaly (increasing splenomegaly) and rising leukocytes unresponsive to therapy.

Definition of blast crisis

  • ≥ 30% blasts in peripheral blood or bone marrow or evidence of extramedullary infiltrates (European LeukemiaNet recommendation).
  • ≥ 20 % blasts (WHO classification).

Note: Patients with 20-29% blasts have a significantly better prognosis than patients with ≥ 30% blasts.

Tyrosine kinase inhibitors (TKi)

Monitoring of response to tyrosine kinase inhibitors.

Investigation time points
Investigation Diagnosis Within the first 3 months After 3 months After 6 months Later
Hematological X Every 2 weeks until CHR X X
  • Every 3 months
  • When clinically necessary
Cytogenetic X X X
  • After 3 months, then every 6 months until CCyR.
  • In case of V. a. TKI resistance.
  • In the case of unclear cytopenia
  • Before change of therapy
Molecular (Q-RT-PCR) X multiplex PCR X X
  • Every 3 months until MMR, then every 3-6 months.
  • Every 4 weeks in the first six months
  • Every 6 weeks in the second half of the year
  • Every 3 months thereafter

Definition of hematologic, cytogenetic, and molecular response.

Method Remission Abbreviation Parameter
Hematological Complete CHR
  • Leukocytes <10 x 109/l
  • Basophils < 5
  • No myelocytes, promyelocytes or myeloblasts in the differential blood count.
  • Platelets < 450 x 109/l
  • Spleen not palpable
Cytogenetic Complete CCyRa No Ph+ metaphases
Partial PCyRa 1-35 % Ph+ metaphases
Minor mCyR 36-65 % Ph+ metaphases
Minimal minCyR 66-95 % Ph+ metaphases
None None CyR > 95% Ph+ metaphases
Molecular Major MMR BCR-ABL transcripts (IS) ≤ 0.1%b
Low MR4 BCR-ABL transcripts ≤ 0.01% or BCR-ABL transcripts 0 with assay sensitivity > 104 (10,000 ABL transcripts).
Low MR4.5 BCR-ABL transcripts ≤ 0.0032% or BCR-ABL transcripts 0 with assay sensitivity > 104.5 (32,000 ABL transcripts).

Definition of inadequate response and resistance to tyrosine kinase inhibitors.

Time after initiation of TKI therapy, months. Response
Hematologic and cytogenetic criteria. PCR criteria
3 No CHR, no CyR
6 > 35 % Ph+, no PCyR > 10 % BCR-ABL (IS)
12 > 0 % Ph+, no CCyR > 1 % BCR-ABL (IS)
Any time
  • Loss of CHR
  • Loss of the CCy
  • Mutations with complete loss of TKI effect.
  • Clonal evolution
  • Loss of MMR
  • Other mutations with reduced TKI binding.

Legend

  • CCyR: complete cytogenetic remission.
  • CHR: complete hematologic remission.
  • IS: international standard
  • MCyR: majore cytogenetic remission.
  • MinCyr: minimal cytogenetic remission
  • MMR: majore (good) molecular remission.
  • PCyR: partial cytogenetic remission.
  • Q-RT-PCR: quantitative polymerase chain reaction.
  • TKI: tyrosine kinase inhibitors.

aPCyR and CCyR together constitute majore cytogenetic remission (MCyR)bQuotient of BCR-ABL to control gene ≤ 0.1% by IS (international standard).