PPROACHES TO THE ASSESSMENT OF MINIMAL RESIDUAL DISEASE IN B-CELL ACUTE LYMPHOBLASTIC LEUKEMIAS IN CONDITIONS OF TARGET THERAPY

Abstract

Background. Flow cytometry (FC) algorithms of detection of minimal residual disease (MRD) are well standardized, and approximate to molecular biologic methods. However, besides informative leukemia-associated aberrant immunophenotype, which are selected taking into account a tumor phenotype at diagnostics stage, it is necessary to consider specificity of the provided taget therapy and its influence on a cell. Objective: to offer stable combinations of antigens to identify B-cell precursors in patients on therapy of blinatumomab. Materials and methods. Clinical observation of patient G. 4 years old with B-cell precursors acute lymphoblastic leukemia (ALL) (pre-pre-B immunosubtype), whom after 3 bloks of reinduction therapy, taking into account MRD-positive status, blinatumomab was appointed as a monotherapy. Tumor immunophenotype was characterized in details by FC protocol according to EuroFlow in debute and relapse of the disease. MRD monitoring was provided by 8-color FC taking into account personalized leukemia-associated aberrant immunophenotypes. Results. In patient with B-cell precursors ALL received blinatumomab, the strategy of MRD monitoring was changed. Due to the lack of CD19 expression, identification of B-cell precursors was based on expression of cyCD22 in combination with nuclear TdT and CD10. Conclusion. In case of blinatumomab’s appointment during B-cell precursors ALL therapy, it is necessary to change the strategy of B-cell precursors identification, due to the lack of CD19 expression. Detection of B-cell precursors should be provided by assessment of other pan-B lineage antigens. First of all, it is cyCD22 or cyCD79a in combination with nuclear TdT and CD10, within the limits of nucleated cells of the sample.