Comparison of different monitoring methods of minimal residual disease in acute lymphoblastic leukemia / 白血病·淋巴瘤

ABSTRACT

The level of minimal residual disease (MRD) is closely associated with prognosis in patients with acute lymphoblastic leukemia (ALL). Currently, 3 kinds of ALL-MRD detection methods commonly used at home and abroad include immunoglobulin heavy chain and T-cell receptor (IGH/TCR) gene rearrangement assessment, flow cytometry (FCM) and leukemia-associated fusion gene detection. IGH/TCR gene rearrangement assessment methods include real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) and next-generation sequencing (NGS). RT-qPCR mainly detects the variable region of IGH/TCR rearrangement genes; it is about one log more sensitive than FCM, but microclones may be easily ignored leading to false negative results. NGS also detects the variable region of IGH/TCR rearrangement genes. The sensitivity of NGS-based MRD assays is higher than that of FCM and RT-qPCR, and its sensitivity is up to 10 -6, while small subclones causing recurrence can be tracked. The sensitivity of MRD was 10 -4 detected by using FCM, while FCM with ≥8-color can achieve 10 -6. However, such high level of sensitivity requires (2-5)×10 7 nucleated cells, which is rarely obtainable from remission marrows. FCM also requires substantial expertise on inspectors, and results may be easily affected by clonal evolution or phenotype shift. RT-qPCR can be used to detect fusion genes such as BCR-ABL, with a sensitivity of up to about 10 -5, but only few ALL patients carry specific gene fusions change that can be used as the monitoring of MRD. For Philadelphia chromosome-positive ALL patients, RT-qPCR is recommended to detect the level of MRD. For Philadelphia chromosome-negative ALL and T-cell ALL patients, FCM, RT-qPCR and NGS methods are all applicable.