LQCL2613 - CMLE - Molecular Diagnosis of Flt3 Mutations in Acute Myeloid Leukemia-LQCL2613

LQCL2613 - Educational Activity

Pdf Summary

This document outlines the importance of molecular testing for FLT3 mutations in acute myeloid leukemia (AML) and how results guide prognosis and treatment. FLT3 mutations occur in ~30–35% of AML, most commonly as internal tandem duplications (FLT3-ITD; ~20–30%) in exons 14–15 and less commonly as tyrosine kinase domain point mutations (FLT3-TKD; ~6–10%), typically in exon 20 at codons D835/I836. Both mutation types cause constitutive activation of the FLT3 receptor, driving leukemogenesis through uncontrolled proliferation and survival signaling.<br /><br />The module reviews key detection methods: PCR fragment analysis (rapid and cost-effective, mainly for ITD sizing), sequencing approaches for TKD (eg, Sanger or allele-specific PCR), next-generation sequencing (NGS) for comprehensive, sensitive detection of ITD/TKD plus other AML-relevant variants, and digital droplet PCR (ddPCR) for highly sensitive detection and quantification, particularly useful for measurable residual disease (MRD) and relapse monitoring. It emphasizes laboratory quality practices including specimen verification, DNA extraction and purity checks, use of positive/negative controls, repeat/confirmatory testing with orthogonal methods, and pathologist oversight.<br /><br />Clinically, FLT3-ITD is strongly associated with higher relapse risk and shorter survival; prognosis is influenced by the FLT3-ITD allelic ratio, with higher ratios (≥0.5) indicating worse outcomes and often prompting consideration of allogeneic stem cell transplant in first remission. FLT3 testing directly informs targeted therapy: midostaurin (with induction chemotherapy) for newly diagnosed FLT3-mutated AML and gilteritinib for relapsed/refractory disease.<br /><br />A case example describes a 42-year-old woman with AML whose NGS testing identified FLT3-ITD with a high allelic ratio (0.8) and no TKD mutation, prompting urgent reporting due to relapse risk. The document highlights ongoing challenges such as mutation heterogeneity, assay sensitivity, and lack of standardization across laboratories.

Keywords

acute myeloid leukemia (AML)

FLT3 mutations

FLT3-ITD

FLT3-TKD (D835/I836)

allelic ratio

molecular testing

next-generation sequencing (NGS)

PCR fragment analysis

digital droplet PCR (ddPCR)

FLT3 inhibitors (midostaurin, gilteritinib)