PF233 CONSISTENCY OF GENOMIC ALTERATIONS ASSESSED BY NEXT‐GENERATION SEQUENCING AMONG CIRCULATING TUMOR DNA, BONE MARROW AND PERIPHERAL BLOOD MONONUCLEAR CELLS IN PEDIATRIC AML
Authors: Ruan M. , Liu C. , Qi B.‐Q. , Chen X.‐Y. , Chang L.‐X. , Zhang A.‐L. , Liu F. , Wang S.‐C. , Liu L.‐P. , Liu X.‐M. , Chen X.‐J. , Zhang L. , Guo Y. , Zou Y. , Zhang Y.‐C. , Chen Y.‐M. , Cao S. , Lou F. , Sun Y. , Zhu X.‐F. 
Published: June 2019

Background:

Acute leukemias are the most common diagnostic group of childhood cancer. Despite constituting only 20% of pediatric acute leukemias, AML (APL excluded) is overtaking acute lymphoblastic leukemia (ALL) as the leading cause of childhood leukemic mortality, suggesting that the precision medicine for pediatric AML needs to be improved. Now the precision therapy for children patients relies on the accurate detection of the mutant spectrum. Bone marrow was commonly used in detecting genetic mutations in the past years, but bone marrow aspiration is invasive procedure and difficult continuous sampling, which severely limited its application in clinical research. Circulating tumor DNA (ctDNA) has emerged as a promising non‐invasive biomarker for gene mutation profiling, and it is easier to realize real‐time monitoring of children patients in clinical practice.

Aims:

The aim of the study was to compare the consistency of the mutation status of ctDNA, peripheral blood mononuclear cell (PBMC) and bone marrow in newly diagnosed pediatric AML patients, and evaluate the feasibility and clinical value of ctDNA testing in pediatric AML.

Methods:

We recruited a total of 20 children patients (13 females and 7 males) admitted to the Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences from May to October 2018. Bone marrow and peripheral blood were taken from all patients at the same time of initial diagnosis stage, while PBMC and ctDNA were isolated from peripheral blood samples. ctDNA, bone marrow and PBMC were sequenced simultaneously to provide a direct comparison of these three sample types.

Results:

Gene mutation detection was performed on bone marrow, PBMC and ctDNA by NGS gene panel approach based on a 185 genes associated to myeloid leukemogenesis. We identified 282 mutations (including 114 indels and 168 SNVs), and 164 out of 282 genetic abnormalities in ctDNA were shared by matched bone marrow and PBMC samples. The consistency among ctDNA, bone marrow and PBMC was 58.2%. When considering the different variant subsets, the consistency of SNVs is higher than indels (68.5% vs 42.3%). Comparing the results of ctDNA with the other two sample types respectively, we observed that the number of mutations coexisted in bone marrow and ctDNA is higher than that in PBMC and ctDNA (64.2% vs 60.1%). But there is a significant correlation (Pearson r = 0.96, 0.96 and 0.97, p < 0.05) in the VAF of concordant mutations between ctDNA and bone marrow, ctDNA and PBMC, and PBMC and bone marrow, indicating that ctDNA had good consistency with bone marrow and PBMC on the VAF of the consistent mutations (figure 1). Besides the shared mutations, the ctDNA samples habored 43 unique mutations that were absent from bone marrow and PBMC samples.

Summary/Conclusion:

This study is the first to demonstrate that ctDNA can be used for mutation detection in pediatric AML. According to the consistency analysis, we observed better concordance of mutations between ctDNA and bone marrow compared to the one between ctDNA and PBMC. Furthermore, the VAF of shared mutations among them highly correlated to each other. In addition, a subset of mutations was exclusively detected in ctDNA, indicating that the genomic landscape derived from ctDNA reflects that from AML to a certain degree.

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