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Karner
March
Acute myeloid leukemias (AMLs) are a heterogeneous group of disorders characterized by the clonal expansion of myeloid blasts (eg, undifferentiated myeloid precursors) in the peripheral blood, bone marrow, and/or other tissues, which results in impaired hematopoiesis and bone marrow failure. AML is the most common acute leukemia in adults; it accounts for approximately 80% of leukemia cases and the largest number of annual leukemia-related deaths in the United States. The median age at diagnosis is 67 years, and 54% of patients are diagnosed at 65 years or older. Advances in the treatment of AML have led to significant improvement in outcomes for younger patients; however, prognosis in the elderly, in whom the majority of new cases occur, remains poor.
The initial laboratory evaluation for AML includes blood chemistry, coagulation studies, and a CBC with a differential of white blood cells (WBCs). In addition to morphologic evaluation of the bone marrow, immunophenotypic, cytogenetic, and molecular genetic ancillary studies are standard of care and are necessary for accurate classification, for risk stratification, and to guide therapy.
Quick Answers for Clinicians
Evaluation of minimal residual disease (MRD) in acute myeloid leukemia (AML) uses two main methodologies. Multiparametric flow cytometry is used to identify leukemia-associated immunophenotypes. Real-time quantitative polymerase chain reaction (qPCR)-based assays target specific leukemia-associated genetic abnormalities that are seen in a subset of patients.
Next generation sequencing (NGS) has made it possible to look at a variety of mutations in multiple genes using a single assay; however, longer turnaround times sometimes limit the incorporation of this information into the routine workup for acute myeloid leukemia (AML). Sensitivity limitations of NGS-based assays currently limit their use in the assessment of minimal residual disease (MRD), although this is rapidly changing.
Indications for Testing
Laboratory evaluation for suspected AML should be considered for individuals who present with signs of bone marrow infiltration (eg, anemia, thrombocytopenia), constitutional symptoms (eg, fever, fatigue, anorexia, weight loss), leukocytosis with circulating peripheral blasts, and/or AML-related complications (eg, tumor lysis syndrome, disseminated intravascular coagulation [DIC], leukostasis).
Laboratory Testing
Diagnosis
The European Leukemia Net (ELN), the National Comprehensive Cancer Network (NCCN), the World Health Organization (WHO), and the European Society for Medical Oncology (ESMO) recommend morphologic assessment of the bone marrow for the initial workup for suspected AML. Bone marrow aspirate and core biopsy enable bone marrow blasts to be enumerated and provide material for ancillary testing, including flow cytometric immunophenotyping, cytogenetics (eg, karyotyping with or without fluorescence in situ hybridization [FISH]), and molecular genetic testing (eg, quantitative polymerase chain reaction [qPCR] and/or next generation sequencing [NGS]). These studies allow for characterization, prognostication, treatment planning, and minimal residual disease (MRD) monitoring.
Immunophenotyping
In AML, flow cytometry is performed to detect leukemic blasts, determine blast lineage, and identify aberrant immunophenotypic features that enable the differentiation of abnormal blast populations from normal progenitors. Flow cytometric immunophenotyping is frequently used in the assessment of MRD after chemotherapy.
Cytogenetics
Cytogenetics are important in the diagnosis, prognosis, treatment, and monitoring of AML. In fact, pretreatment cytogenetic abnormalities constitute the single strongest prognostic factor for complete remission (CR) and overall survival (OS) in AML. The WHO 2016 classification defines acute leukemia as ≥20% blasts in the marrow or peripheral blood; however, a diagnosis of AML may be made with <20% blasts in patients with certain recurrent cytogenetic abnormalities [eg, t(15;17), t(8;21), t(16;16), inv(16)].
Cytogenetic testing methodologies include karyotyping and FISH. Karyotyping, also known as chromosomal analysis, is used to identify recurrent cytogenetic abnormalities. FISH is more sensitive than karyotyping for detecting potentially cryptic cytogenetic aberrations.
| Translocation | Frequency | Prognosis | Predictive Factors |
|---|---|---|---|
t(8;21)(q22;q22.1) RUNX1-RUNX1T1 | 1-5% of AML cases More common in younger patients | Usually associated with a high rate of CR and long-term, disease-free survival when treated with intensive consolidation therapy (eg, high-dose cytarabine) | Adverse KIT mutations in adults CD56 expression |
inv(16)(p13.1;q22) or t(16;16)(p13.1;q22) CBFB-MYH11 | 5-8% of cases in younger patients Lower frequency in older adults | Usually associated with a high rate of CR and favorable OS when treated with intensive consolidation therapy (eg, high-dose cytarabine) | Improved Chromosome 22 gain (as secondary abnormality) Adverse KIT mutations (especially involving exon 8) in adults Older age Increased WBCs FLT3 mutations (especially tyrosine kinase domain mutation, FLT-TKD) Trisomy 8 |
Acute promyelocytic leukemia t(15;17)(q22;q11-12) PML-RARA | 5-8% of cases in younger patients Disease can occur at any age, but most patients are middle-aged adults Lower frequency in older adults | Has more favorable prognosis when treated appropriately (with a combination of tretinoin and arsenic trioxide, with or without anthracycline for high-risk patients) than any other AML cytogenetic subtype | Adverse Coagulopathy (associated with significant early death rates) Hyperleukocytosis CD56 expression FLT3-ITD mutation Older age Note: The significance of these features with current therapy is unclear |
t(9;11)(p21.3;q23.3) KMT2A-MLLT3 | 9-12% of AML cases in children 2% of AML cases in adults Can occur at any age, but is more common in children | Generally intermediate survival, superior to that seen in AML with other 11q23.3 translocations Note: Cases with t(9;11) and <20% blasts are not currently classified as AML (although this is controversial), but may be treated as such if clinically appropriate | Adverse MECOM overexpression |
t(6;9)(p23;q34.1) DEK-NUP214 | 0.7-1.8% of AML cases Occurs in both children and adults Median pediatric patient age is 13 yrs; median age in younger adults is 35-44 yrs | Generally poor prognosis in both children and adults Note: Cases with t(6;9)(p23;q34.1) and <20% blasts are not currently classified as AML (although this is controversial), but may be treated as such if clinically appropriate | Improved Allogeneic hematopoietic stem cell transplant (may be associated with better OS) Adverse Increased WBCs (most predictive of shorter OS) Increased bone marrow blasts (associated with shorter disease-free survival) |
inv(3)(q21.3;q26.2) or t(3;3)(q21.3;q26.2) GATA2, MECOM | 1-2% of AML cases Occurs most commonly in adults No sex predilection | Aggressive disease with short survival Outcome with <20% or >20% blasts is similarly poor Cases with <20% blasts are not currently classified as AML (although this is controversial), but may be treated as such if clinically appropriate | Adverse Complex karyotype and additional monosomy 7, regardless of blast percentage, are associated with a worse prognosis |
Megakaryoblastic AML t(1;22)(p13.3;q13.1) RBM15-MKL1 | Less than 1% of AML cases Restricted to infants and young children (≤3 yrs); most cases occur in the first 6 mos of life (median patient age, 4 mos) Uncommon abnormality in AML; when present, most commonly occurs in infants without trisomy 21 Female predominance | High-risk disease compared with pediatric acute megakaryocytic leukemia without t(1;22) | — |
t(9;22)(q34.1;q11.2) BCR-ABL1 | <1% of AML cases Occurs primarily in adults Possible male predominance | Aggressive disease with poor response to traditional AML therapy or TKI therapy alone | Improved TKI therapy followed by allogeneic hematopoietic cell transplant |
| AML-MRC | |||
| AML-MRC | 24-35% of all AML cases Occurs primarily in the elderly Rare in children | Generally has a poor prognosis with a lower rate of CR than other AML subtypes | Improved Previous MDS cases with relatively low blast counts may constitute less clinically aggressive disease Previous MDS cases with 20-29% bone marrow blasts may behave in a manner more similar to that of MDS than other AMLs Adverse In the absence of a CEBPA double mutation or NPM1 mutation, multilineage dysplasia still appears to confer a poor prognosis, although not as poor as the prognosis for cases with high-risk cytogenetic abnormalities ASXL1 mutations may be associated with a worse prognosis CD14 expression CD11b expression |
| t-MNs | |||
| t-MNs | 10-20% of all cases of AML, MDS, and MDS/MPN Most patients have been treated for a previous malignancy 70% of patients have been treated for a solid tumor (breast cancer most common) 30% of patients have been treated for a hematologic neoplasm (non-Hodgkin lymphoma is most common) 5-20% of t-MN cases occur after therapy for a nonneoplastic disorder | Poor 5-yr survival rates (<10%) | Improved Cases with balanced chromosomal translocations generally have a better prognosis; however, such cases, except those with t(15;17) and inv(16) or t(16;16), have shorter median survival times than their de novo counterparts Adverse Cases associated with abnormalities in chromosomes 5 and/or 7, TP53 mutations, and a complex karyotype have a particularly poor outcome, with a median survival time of <1 yr |
AML-MRC, AML with myelodysplasia-related changes; ITD, internal tandem duplication; MDS, myelodysplastic syndrome; MPN, myeloproliferative neoplasm; TKD, tyrosine kinase domain; TKI, tyrosine kinase inhibitor; t-MNs, therapy-related myeloid neoplasms | |||
Molecular Genetics
Gene alterations, along with translocations and inversions, carry prognostic importance in AML. In addition to large chromosomal rearrangements, molecular changes have also been implicated in the development of AML. In fact, genetic mutations are identified in more than 97% of cases, often in the absence of any large chromosomal abnormality. A comprehensive evaluation of several molecular markers (eg, FLT3, NPM1, CEBPA, KIT, IDH1, and IDH2) is important for risk assessment and prognostication in certain patients with AML and may guide treatment decisions.
Monitoring
Monitoring relies on knowledge of the leukemia-associated phenotype defined at diagnosis for the detection of MRD. The most frequently used methods for monitoring include flow cytometry for abnormal immunophenotypes and PCR-based assays to detect previously identified mutations.
ARUP Laboratory Tests
Flow Cytometry
Giemsa Band
Specimen: bone marrow
Giemsa Band/Genomic Microarray (Oligo-SNP array)
Specimen: bone marrow
Giemsa Band/Genomic Microarray (Oligo-SNP array)
Specimen: leukemic blood
Fluorescence in situ Hybridization (FISH)
Specimen: bone marrow, whole blood
Fluorescence in situ Hybridization (FISH)
Fluorescence in situ Hybridization (FISH)
Specimen: bone marrow, whole blood
Probes include -5/del(5q); -7/del(7q); and 11q23 rearrangements (targets MLL)
Fluorescence in situ Hybridization (FISH)
Specimen: bone marrow, whole blood (when hyperleukocytosis is present and bone marrow aspiration is not possible)
PML probe targets the PML gene (15q22); RARA probe targets the RARA gene (17q21.1)
Reverse Transcription Polymerase Chain Reaction
Specimen: bone marrow (preferred for maximum sensitivity), whole blood
Quantitative Reverse Transcription Polymerase Chain Reaction
Specimen: bone marrow (preferred for maximum sensitivity), whole blood
Reverse Transcription Polymerase Chain Reaction
Specimen: bone marrow (preferred for maximum sensitivity), whole blood
Quantitative Reverse Transcription Polymerase Chain Reaction
Specimen: bone marrow, whole blood
Capillary Electrophoresis
Massively Parallel Sequencing
Massively Parallel Sequencing
Specimen: bone marrow, whole blood
Components: ANKRD26, ASXL1, CEBPA, DDX41, DNMT3A, ETV6, FLT3, GATA2, IDH1, IDH2, KIT, KRAS, NPM1, NRAS, RUNX1, TP53, WT1
Massively Parallel Sequencing
Specimen: bone marrow, whole blood
Components: ANKRD26, ASXL1, ASXL2, BCOR, BCORL1, BRAF, CALR, CBL, CBLB, CEBPA, CSF3R, CUX1, DDX41, DNMT1, DNMT3A, EED, ELANE, ETNK1, ETV6, EZH2, FAM5C, FBXW7, FLT3, GATA1, GATA2, GNAS, HNRNPK, IDH1, IDH2, IL7R, JAK1, JAK2, JAK3, KDM6A, KIT, KMT2A, KRAS, LUC7L2, MAP2K1, MLL, MPL, NOTCH1, NPM1, NRAS, NSD1, PHF6, PIGA, PRPF40B, PRPF8, PTPN11, RAD21, RUNX1, SETBP1, SF1, SF3A1, SF3B1, SH2B3, SMC1A, SMC3,SRSF2, STAG2, STAT3, STAT5B, SUZ12, TET2, TP53, U2AF1, U2AF2, WT1, ZRSR2 (one or more exons of the preferred transcript are not covered by sequencing for CUX1, DNMT1, KDM6A, NPM1, STAT5B, SUZ12)
Massively Parallel Sequencing
Massively Parallel Sequencing
Specimen: cultured skin fibroblasts (preferred), whole blood, skin punch biopsy
Components: ANKRD26, ATM, BLM, CBL, CEBPA, DDX41, ELANE, ETV6, GATA1, GATA2, KRAS, NBN, PTPN11, RUNX1, SAMD9, SAMD9L, SRP72, TERC, TERT, TP53
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Specimen: bone marrow, whole blood, tissue, fluid