Flow cytometric minimal residual disease assessment in B‐cell precursor acute lymphoblastic leukaemia patients treated with CD19‐targeted therapies — a EuroFlow study

Abstract

Summary The standardized EuroFlow protocol, including CD19 as primary B‐cell marker, enables highly sensitive and reliable minimal residual disease (MRD) assessment in B‐cell precursor acute lymphoblastic leukaemia (BCP‐ALL) patients treated with chemotherapy. We developed and validated an alternative gating strategy allowing reliable MRD analysis in BCP‐ALL patients treated with CD19‐targeting therapies. Concordant data were obtained in 92% of targeted therapy patients who remained CD19‐positive, whereas this was 81% in patients that became (partially) CD19‐negative. Nevertheless, in both groups median MRD values showed excellent correlation with the original MRD data, indicating that, despite higher interlaboratory variation, the overall MRD analysis was correct.

Reliable Flow-Cytometric Approach for Minimal Residual Disease Monitoring in Patients with B-Cell Precursor Acute Lymphoblastic Leukemia after CD19-Targeted Therapy

“…Based on the published data from other groups [ 15 , 16 , 17 , 50 ] and our consecutive studies [ 18 , 19 , 20 , 22 , 23 , 24 ], we have developed, validated and implemented an 11-color single-tube approach for MFC-MRD detection in routine practice. Ready-to-use premanufactured tubes containing the majority of used antibodies can seriously improve the reliability of the assay by minimizing possible pipetting errors and providing highly stable cytometric data, which can be analyzed not only manually but also with programmed approaches [ 28 , 51 , 52 ].…”

“…The use of iCD79a as a solid antigen for the B-cell compartment [ 16 ] also has limitations, because intracellular staining in samples from heavily pretreated patients could lead to equivocal distribution between positive and negative cells, which can be overcome by the use of other B-cell markers in combination with iCD79a, as we suggest. The currently known EuroFlow approach [ 17 ] is a modification of their conventional panels and gating algorithms. This modification is mainly based on CD10 and CD34 expression, which is sometimes not total even in diagnostic samples.…”

“…This modification is mainly based on CD10 and CD34 expression, which is sometimes not total even in diagnostic samples. Nevertheless, it was announced that the new MFC-MRD methodology for after CD19-directed immunotherapy designed by the EuroFlow consortium will be published soon [ 17 ].…”

“…Currently, there is no consensus approach to MFC-MRD monitoring after blinatumomab or CAR-T therapy for BCP-ALL. There are several described changes in the MFC-MRD methodology, including the addition of other early B-lineage antigens [ 15 , 16 ] or only the modification of the gating algorithm using conventional sets of antibodies [ 17 ]. Based on our previously obtained data, we aimed to develop an antibody panel and MFC data analysis algorithm, which is a reliable method for MFC-MRD detection in patients with BCP-ALL treated with a CD19-directed treatment.…”

B‐lineage antigens that are useful to substitute CD19 for minimal residual disease monitoring in B cell precursor acute lymphoblastic leukemia after CD19 targeting

“…Wide implementation of CD19‐directed treatment either with blinatumomab or with T‐lymphocytes harboring chimeric antigen receptor against CD19 results in the necessity of new approach development due to frequent loss of CD19 by tumor cells under the pressure of targeting (Libert et al, 2020; Mikhailova, Gluhanyuk, et al, 2021; Mikhailova, Illarionova, et al, 2022). Currently, one can find suggestions for both inclusion of additional B‐lineage markers in MFC‐MRD antibody combinations (Chen et al, 2021; Cherian et al, 2018) and adaptations of conventional antigen sets for the possible lack of key gating antigens (Mejstrikova et al, 2017; Verbeek et al, 2021).…”