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FLT3 Mutation Analysis

Test code(s) 39786

Question 1. What does the FLT3 Mutation Analysis test for?

This test detects activating mutations in the gene encoding FMS-like tyrosine kinase 3 gene, a receptor tyrosine kinase that plays a significant role in cell survival, proliferation, and differentiation of hematopoietic stem cells. DNA extracted from peripheral blood or bone marrow is tested for internal tandem duplications (ITDs) and tyrosine kinase domain (TKD) mutations involving codons 835 and 836 in FLT3.

Question 2. What is the clinical significance of this test?

Mutations of FLT3 represent some of the most frequent molecular changes in acute myeloid leukemia (AML) and are reported in 25% to 30% of AML patients.1 These mutations include FLT3 ITDs in the region encoding the juxtamembrane region of FLT3 and point mutations in the TKD; these mutations promote malignancy by constitutively activating FLT3 kinase activity without the need for the ligand. FLT3-ITD mutations with a high mutant allelic ratio (≥0.5) are associated with a poor prognosis, high relapse rates, and reduced overall survival.2  Patients with FLT3 mutation−positive AML, both ITD and TKD, could be eligible for FDA-approved targeted therapies such as midostaurin.1

Question 3. How is the assay performed, and what is its analytical sensitivity for mutation detection?

The assay detects ITDs and TKD mutations in the FLT3 gene using polymerase chain reaction (PCR) coupled with fragment analysis.3,4 The assay can detect these mutations when present in as few as 5 cells in a background of 100 total cells.

Question 4. What types of specimens are acceptable for this test?

The preferred specimen type is whole blood or bone marrow aspirate in an EDTA tube. Heparin tubes may be submitted but are not preferred. DNA extracted in a CLIA laboratory is also acceptable.

Question 5. How long will it take to receive results?

Results can be expected in 3 to 4 days after specimen receipt.

Question 6. How is this test different from the FLT3 testing done in the LeukoVantage®, Myeloid and the LeukoVantage®, Acute Myeloid Leukemia (AML) tests?

This test detects the FLT3 ITD and TKD mutations using PCR-fragment analysis. In both LeukoVantage assays, next-generation sequencing is used to test for mutations in FLT3 as a part of a panel of additional genes with known clinical significance in myeloid neoplasms. This test and the LeukoVantage myeloid and AML tests all detect same clinically significant mutations in FLT3; however, the LeukoVantage tests could provide better sequence-related details for the ITD and TKD mutations detected.  

Question 7. How is this test different from the LeukoStrat® CDx FLT3 Mutation Assay?

Both tests use PCR-fragment analysis to detect the same FLT3 ITD and TKD mutations in FLT3; however, the LeukoStrat CDx FLT3 Mutation Assay (test code 90574) is FDA-approved for use as an aid in the selection of patients with AML for whom the drug midostaurin is being considered.5

References

  1. Daver N, Schlenk RF, Russel NH, et al. Targeting FLT3 mutations in AML: review of current knowledge and evidence. Leukemia. 2019;33(2):299-312. doi:10.1038/s41375-018-0357-9
  2. Cuervo-Sierra J, Jaime-Pérez JC, Martínez-Hernández RA, et al. Prevalence and clinical significance of FLT3 mutation status in acute myeloid leukemia patients: a multicenter study. Arch Med Res. 2016;47(3):172‐179. doi:10.1016/j.arcmed.2016.06.003
  3. Murphy KM, Levis M, Hafez MJ, et al. Detection of FLT3 internal tandem duplication and D835 mutations by a multiplex polymerase chain reaction and capillary electrophoresis assay. J Mol Diagn. 2003;5(2):96-102. doi:10.1016/S1525-1578(10)60458-8
  4. 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(8):2434-2439. doi:10.1182/blood.V97.8.2434
  5. RYDAPT® (midostaurin). Highlights of prescribing information. Novartis Pharmaceuticals Corporation; 2017.
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.221 Version: 1
Version 1: Effective 02/01/2021 to present
Version 0: Effective 11/30/2020 to 02/01/2021