Flow cytometric assessment for minimal/measurable residual disease in B lymphoblastic leukemia/lymphoma in the era of immunotherapy

Abstract

Minimal/measurable residual disease (MRD) is the most important independent prognostic factor for patients with B‐lymphoblastic leukemia (B‐LL). MRD post therapy has been incorporated into risk stratification and clinical management, resulting in substantially improved outcomes in pediatric and adult patients. Currently, MRD in B‐ALL is most commonly assessed by multiparametric flow cytometry and molecular (polymerase chain reaction or high‐throughput sequencing based) methods. The detection of MRD by flow cytometry in B‐ALL often begins with B cell antigen‐based gating strategies. Over the past several years, targeted immunotherapy directed against B cell markers has been introduced in patients with relapsed or refractory B‐ALL and has demonstrated encouraging results. However, targeted therapies have significant impact on the immunophenotype of leukemic blasts, in particular, downregulation or loss of targeted antigens on blasts and normal B cell precursors, posing challenges for MRD detection using standard gating strategies. Novel flow cytometric approaches, using alternative strategies for population identification, sometimes including alternative gating reagents, have been developed and implemented to monitor MRD in the setting of post targeted therapy.

15‐color highly sensitive flow cytometry assay for post anti‐CD19 targeted therapy (anti‐CD19‐CAR‐T and blinatumomab) measurable residual disease assessment in B‐lymphoblastic leukemia/lymphoma: Real‐world applicability and challenges

“…The analysis strategy of an MFC‐BMRD approach completely depends on gating the target cells for focused and deeper subsequent analysis. CD19 has been traditionally used for this purpose due to its consistent expression throughout most parts of the B cell maturation 11,13,40 . Recently, CD19‐directed therapies, including blinatumomab and anti‐CD19‐CAR‐T, have improved the outcomes of relapsed/refractory B‐ALL 43–45 .…”

“…We designed a 15‐color BMRD assay incorporating markers based on our previous experiences and published literature review 2,13,28,39,40 . Details of the antibody panel are given in Table 1.…”

“…We designed a 15-color BMRD assay incorporating markers based on our previous experiences and published literature review. 2,13,28,39,40 Details of the antibody panel are given in Table 1. The purpose of antibodies included in this panel can be grouped into: (control samples) bi-weekly and also with the freshly prepared cocktail at the end of 6th week.…”

Issue highlights—May 2023

“…Therefore, use of these therapies pose great challenges for clinical cytometry labs in the assessment of post-treatment samples, especially in the detection of measurable/ minimal residual disease (MRD). In this issue, Chen, Gao, et al (2023) provided an overview of MRD detection in B-lymphoblastic leukemia/ lymphoma in the era of immunotherapy, and Gao et al (2023) focused their review on the impact of targeted therapy on mature B-and plasma cell neoplasms utilizing flow cytometry assessments. In both reviews, the authors illustrated the challenges, identified the problems, and provided a list of available options and solutions.…”

Issue highlights—July 2023

“…Targeted immunotherapy demonstrated encouraging results in recent years but induces significant changes in the phenotype of leukemic blasts concurrently. Therefore, alternative gating strategies have gained importance and potential CD19 substitutes have been proposed (Chen et al, 2023; Mikhailova et al, 2022).…”