Determination of the FLT3-ITD mutation by two methods in patients with acute myeloblastic leukemia: comparison and implementation of a new method

Abstract

Constitutive activation in the absence of FLT3 receptor ligand (FMS-like tyrosine kinase 3) occurs with high frequency in acute myeloid leukemia (AML) due to two types of mutations in its gene: internal tandem duplications (ITD) that affect the juxtamembrane region, or point mutations that affect the tyrosine kinase domain (TKD). The first one is associated with an unfavorable prognosis, whereas the second type gives inconclusive results.

In this work, two methods are compared for the detection of FLT3-ITD: polymerase chain reaction followed by agarose gel electrophoresis (PCR+AGE) and polymerase chain reaction followed by fragment analysis (PCR+FA), the additional information provided by the latter methodology is evaluated and the mutational state of the FLT3 gene is correlated with multiple variables.

We studied 63 patients with AML in search of the FLT3-ITD mutation by both methods. There was good agreement between the techniques (k = 0.85). Two false negatives were detected by PCR+AGE, as well as an indeterminate result. Based on the quantitative assay, PCR+FA, the allelic ratios found were from 0.05 to 7.7 (median 0.81) and ITD length ranged from 16 to 174 (median 34). The frequency of appearance of the mutation was 20.6%, with predominance in patients with subtype FAB M2. No significant differences were found in the count of leukocytes, neutrophils, platelets, hemoglobin and blasts in peripheral blood between carriers and non-carriers of the mutation. The overall survival of the FLT3-ITD+ patients was significantly lower, with a relative risk of death at 6 months of 1.45.

The relevant extra information provided by the PCR+FA compared with PCR+AGE, the simplicity and limited time of its procedure show it as a strong technique for forecasting the disease and redefining risk, and feasible to implement in the clinical laboratory.