A laboratory developed diagnostic test for detection of internal tandem duplications in the juxtamembrane domain (ITD) and a missense mutation (D835) in the kinase domain of the FLT3 gene (TKD).
Background:
FLT3 plays a key role in cell survival, proliferation, and differentiation of hematopoietic stem cells. Two major mutation types that result in ligand-independent activation of the FLT3 receptor have been described: internal tandem duplications (ITD) and point mutations at codon D835 within the activation loop of the tyrosine kinase domain (TKD). The presence of ITD mutations in cytogenetically normal AML is associated with a poorer prognosis compared to cytogenetically normal AML without the mutation when treated with current standard chemotherapy. The prognostic significance of FLT-TKD is less certain.
Methodology & Reporting:
For detection of ITD mutations, DNA is subjected to PCR amplification using primers targeting the juxtamembrane domain of FLT3, and products are analyzed by capillary electrophoresis. The D835 mutation is assessed by PCR amplification using primers flanking the mutation site followed by restriction fragment length polymorphism analysis. The analytical sensitivity of this assay is 5% for FLT3-ITD and 10% for FLT3-TKD, which is relatively similar to the analytical sensitivity of our reference lab, Mayo Medical laboratories’ assay. Mutation status will be reported as positive or negative. If an ITD mutation is detected, an allelic ratio will be reported as well. This test is not intended for monitoring residual disease following treatment.
Specimen requirement and testing information:
Specimen: Whole blood, Bone marrow aspirate
Test Code: FLT3
CPT Code: 81245, 81246
Turnaround time (TAT): 3-7 days
References:
Gilliland DG, Griffin JD. The role of FLT3 in hematopoiesis and leukemia. Blood. 2002;100(5), 1532-1542
Thiede C, Steudel C, Mohr B, et al. Analysis of FLT3-activating mutations in 979 patients with acute myelogenous leukemia: association with FAB subtypes and identification of subgroups with poor prognosis. Blood. 2002;99(12):4326–4335
Frohling S, Schlenk RF, Breitruck J, et al. Prognostic significance of activating FLT3 mutations in younger adults (16 to 60 years) with acute myeloid leukemia and normal cytogenetics: a study of the AML Study Group Ulm. Blood. 2002;100(13):4372–4380
Schnittger S, Schoch C, Dugas M, et al. Analysis of FLT3 length mutations in 1003 patients with acute myeloid leukemia: correlation to cytogenetics, FAB subtype, and prognosis in the AMLCG study and usefulness as a marker for the detection of minimal residual disease. Blood. 2002;100(1):59–66
Meshinchi S, Woods WG, Stirewalt DL, et al. Prevalence and prognostic significance of Flt3 internal tandem duplication in pediatric acute myeloid leukemia. Blood. 2001;97(1):89–94
Liang DC, Shih LY, Hung IJ, et al. Clinical relevance of internal tandem duplication of the FLT3 gene in childhood acute myeloid leukemia. Cancer. 2002;94(12):3292–3298
Yamamoto Y, Kiyoi H, Nakano Y, et al. Activating mutation of D835 within the activation loop of FLT3 in human hematologic malignancies. Blood. 2001;97:2434-9
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