Multidimensional Study on the Prognostic Factors of Acute Myeloid Leukemia Patients with FLT3-ITD mutations Based on the Next-Generation Sequencing Platform

Purpose: This research aimed to investigate the features and effects of FLT3-ITD mutations in Chinese acute myeloid leukemia (AML) population, and to explore whether ITD variant allele frequency (VAF), number of mutations, insertionposition and length will have influence on the patients' overall survival (OS) and relapse-free survival (RFS).

Methods:A total of 101 newly diagnosed AML (non-APL) patients with FLT3-ITD mutations from December 2013 to March 2018 were recruited. Their bone marrow or peripheral blood samples were sequenced by NGS 185-gene platform, then the sequencing data were analyzed in combination with the patients' clinical information.

Results:The most common concomitant mutations in FLT3-ITD patients were NPM1, DNMT3A, TET2, IDH2, RUNX1, and WT1. The patients' median VAF is 0.344 (0.084-0.487). Among 101 patients, 80 (79.2%) carried 1 ITD mutation, 17 (16.8%) carried 2, 3 (3.0%) carried 3, and only 1 (1.0%) carried 4. In most patients (76/101) the ITD fragments were inserted in the JM region. And the median length of the insertion fragments was 54 (12-252) bp. According to the NCCN guidelines 2018, the cutoff value of FLT3-ITDmutation VAF between different stages of prognosis is 0.33. However, in our research, it was better to set 0.30 (p=0.0465 for OS; p=0.4929 for RFS), but not 0.33 (p=0.4270 for OS; p=0.3828 for RFS), as the cutoff value to tell differences of survival. Meanwhile, the numbers of carried ITD was significantly related to prognosis. The patients with single ITD mutation were found to have better clinical outcomes than those with multiple ITD mutations (p= 0.0031 for OS; p=0.0001 for RFS). Patients with ITD insertion in the hinge region of JM had a trend of poorer OS. The insertion length of ITD fragment correlated with the patients' RFS, but not OS. The longer the insertion was, the worse RFS of the patient showed (p=0.0323, p trend=0.0049).

Conclusion:The VAF, the number of mutations, and the insertion length of the FLT3-ITDmutations will significantly affect the prognosis of AML patients in Chinese population.