Recently, Professor Xiaofan Zhu, Director of the Division of Pediatric Hematology and Oncology Center at the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences, Associate Chief Physician Doctor Min Ruan and Attending Doctor LiPeng Liu collaborated on a study titled "Early Detection of Minimal Residual Disease and Risk Stratification for Children with Acute Myeloid Leukemia via Circulating Tumor DNA," published in Clinical Cancer Research (with an impact factor of 11.5). This prospective study was the first to evaluate the longitudinal changes of ctDNA from plasma in patients, as compared to NGS based bone marrow DNA, for the early detection of relapse in children with AML.

Minimal residual disease (MRD) detection and risk stratification are pivotal in the management of acute myeloid leukemia (AML) in children. Traditional methods such as flow cytometry, qPCR, and NGS have limitations that necessitate the development of more effective techniques. Circulating tumor DNA (ctDNA) testing offers a promising alternative due to its minimally invasive nature and potential for early relapse detection and monitoring of treatment response. This study investigates the utility of ctDNA as a novel predictive and prognostic biomarker in AML treatment for children, highlighting its advantages over traditional methods.

Background

MRD is a dynamic measure of disease burden during therapy, serving as a significant prognostic factor even in patients without morphologically detectable blasts. Traditional methods for MRD detection, such as flow cytometry, quantitative PCR (qPCR), and next-generation sequencing (NGS), have various limitations. Flow cytometry, while widely applied, has low precision, and patients with undetectable MRD by this method may still relapse. qPCR can detect rare residual leukemia cells but evaluates a limited number of markers, potentially missing emerging subclones. NGS, although highly sensitive and able to target a wide range of genetic markers, is expensive and impractical for serial monitoring.

Bone marrow sampling, commonly used for these methods, is invasive and carries potential risks. Therefore, there is a pressing need for a validated method for MRD assessment that covers a range of variants and is less invasive. Liquid biopsy, or blood sampling, offers a convenient and safe alternative, with ctDNA testing emerging as a significant method in this context.

Therefore, there is still a great need for us to investigate a validated method for mMRD assessment in a range of variants among AML patients. Blood sampling, known as  liquid biopsy, is warranted due to its convenience and safety. ctDNA testing has been introduced in cancer care, becoming increasingly prevalent in recent years, including for both solid tumors and haematological malignancies.

Methods and Study Design

Cancer cells release DNA fragments into the bloodstream. ctDNA testing detects these fragments via blood draws and is increasingly used in cancer care to assess relapse risk and monitor therapy response. However, the variety of ctDNA testing methods, including the relatively new ddPCR technology, requires clear guidelines for use. The concordance between blood and bone marrow ctDNA samples remains under investigation.

This study aims to examine the role of ctDNA as a novel predictive and prognostic biomarker in the serial monitoring of tumor burden and treatment response in children with AML. Utilizing ddPCR method, a prospective longitudinal study is conducted to investigate the dynamic changes in plasma ctDNA compared to NGS-based bone marrow DNA analysis during treatment.

A total of 50 pediatric AML patients are enrolled. Baseline bone marrow aspirations are performed at diagnosis, with sequential evaluations at specific chemotherapy cycles. Plasma samples for ctDNA analysis were collected simultaneously. The study’s primary outcome is to investigate the concordance of variant allele frequency (VAF) of mutations between bone marrow DNA and ctDNA. Secondary outcomes includes progression-free survival (PFS) and overall survival (OS).

Findings or Results

The study observed a 93% concordance rate of patient-specific tumor mutations between ctDNA and bone marrow DNA, with similar VAFs observed in both concordant and discordant mutations. This suggests that differences in tumor mutation frequencies were unlikely to account for discrepancies between the two methods. A head-to-head comparison between ctDNA and flow cytometry-based MRD detection showed a significant correlation in mutation VAF between the two methods. This further validates ctDNA’s utility as a reliable MRD detection method. The study found that patients who cleared their ctDNA had significantly improved overall survival (OS) and progression-free survival (PFS) compared to those with detectable ctDNA at the end of the fourth chemotherapy cycle. Specifically, patients with undetectable ctDNA after initial chemotherapy, which remained undetectable or decreased significantly by the fourth cycle, had a favorable prognosis. Conversely, patients with persistent or newly positive ctDNA showed significantly lower PFS, underscoring ctDNA’s predictive value in treatment response and prognosis. The study also explored the threshold of ctDNA in differentiating prognosis, finding that patients with a VAF reduction of more than three logs, even without complete clearance, had improved PFS similar to those who cleared their ctDNA.

Significance of the Research

The research highlights the significant potential of ctDNA profiling in improving MRD detection, reducing the need for invasive bone marrow sampling, and providing more accurate risk stratification. These advancements can lead to more personalized and effective treatment plans, ultimately improving survival rates and quality of life for pediatric AML patients.

Conclusion

The study concludes that ctDNA profiling during treatment can effectively stratify AML patients into favorable and unfavorable prognostic groups. This prospective study is the first to evaluate longitudinal changes in patient-tailored ctDNA from plasma compared to NGS-based bone marrow DNA for early relapse detection in children with AML. The findings highlight ctDNA’s potential as a less invasive, reliable biomarker for MRD detection and risk stratification, paving the way for its broader clinical application in pediatric AML management.

Reference

1.     Haematologica. 2022;107(12):2810-2822.

2.     Kim YJ. J Hematol Oncol. 2024;17(1):10.

Professor  Xiaofan Zhu

Director of the Division of Pediatric Hematology and Oncology Center at the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences

Chief Physician, Doctoral Supervisor

Vice Chairman of the Pediatric Hematology and Oncology Committee of the Chinese Anti-Cancer Association

Head of the Hematology Group of the Tianjin Medical Association’s Pediatric Branch

Vice Chairman of the Tianjin Pediatric Tumor Committee

Editorial Board Member of “Chinese Journal of Pediatrics,” “Chinese Journal of Hematology,” “Contemporary Pediatrics in China,” and other journals

Has undertaken multiple national and provincial-level research projects. Awarded the National Natural Science Award, the First Prize of Tianjin Natural Science, the Wuzhou Women’s Science and Technology Award, Song Qingling Pediatric Medical Award, and other honors. Published over a hundred papers, and in the past five years, has published numerous papers as the first and corresponding author in journals such as “Nature Genetics,” “JAMA Oncology,” “Lancet Oncology,” “Nature Cell Biology,” “Nucleic Acids Research,” “Blood,” “BMC Medical Genomics,” etc.

Min Ruan

MD, Associate Chief Physician, Division of Pediatric Hematology and Oncology Center, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences

Focus on the clinical research in pediatric AML

Member of the Hematology and Oncology Committee of the Tianjin Anti-Cancer Association

Member of Stem Cell and Translational Medicine Committee of Tianjin Integrative Medicine Society

Secretary of Pediatric AML Working Group of Children’s Blood Disease Alliance, National Clinical Research Center for Blood Diseases

Lipeng Liu

MD, Attending doctor, Division of Pediatric Hematology and Oncology Center, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences

Focus on the clinical and basic researches in pediatric hematology and oncology

Publications

Early detection of molecular residual disease and risk stratification for children with acute myeloid leukemia via circulating tumor DNA, Clinical Cancer Research, 2024;30(6):1143-1151.

Development and validation of a prognostic scoring model to risk stratify childhood acute myeloid leukaemia. British Journal of Haematology, 2022, 198(6): 1041-1050

High risk of bloodstream infection of carbapenem-resistant enterobacteriaceae carriers in neutropenic children with hematological diseases, Antimicrobial Resistance & Infection Control, 2023, 12(1): 66