Significance of multicolor flow cytometry in the detection of minimal residual disease in monitoring CD19-CAR-T cell bridging allo-HSCT treatment of B-ALL patients / 中华检验医学杂志

ABSTRACT

Objective:To investigate the significance of multicolor flow cytometry (MFC) monitoring of minimal residual disease (MRD) in the course of allogeneic hematopoietic stem cell transplantation (allo-HSCT) after CD19-chimeric antigen receptor(CAR)-T cell immunotherapy for patients with refractory, relapsed B-cell acute lymphoblastic leukemia (r/r B-ALL).Methods:37 patients with r/r B-ALL admitted to Hebei Yanda Lu Daopei Hospital from January to July 2019, aged 15 (6, 19) years old, including 24 males and 13 females, were treated with CD19-CAR-T cell immunotherapy bridging allo-HSCT. MFC with cytoplasmic CD79a antibody to set up B-cell gates was used to monitor patients′ bone marrow (BM), cerebrospinal fluid (CSF), and tissue samples on day 0 (prior to the CAR-T cell immunotherapy), day 15, day 28 post CAR-T cell immunotherapy, and post transplantation.The MRD values of these samples were analyzed to evaluate the residual tumor cells and metastasis. The killing effect of the CAR-T cells was evaluated by the recovery of CD19+B cells before transplantation and the period between the timepoint when CD19+B cells was recovered and the timepoint when CAR-T cells were infused. Peripheral blood CAR-T cells were counted at different time points. Statistic analysis was performed by Kaplan-Meie assay and Log-rank test to analyze the difference of univariate cumulative survival.Results:(1)Among the 37 patients, 8 died and 29 survived. 5 patients relapsed after transplantation, of which 4 relapsed patients died and 1 survived. (2)MFC MRD negative remission rate of the death group was lower than that of the survival group at the following time points post-CAR-T therapy and prior to transplantation (5/8 vs. 28/29, χ 2=7.540, P=0.006); day 15 of the CAR-T cell reinfusion (3/8 vs. 24/29, χ 2=6.512, P=0.011); day 28 of the reinfusion (3/8 vs. 276/29, χ 2=10.065, P=0.002). The probability of extramedullary MFC MRD positive tumor infiltration in the death group was higher than that in the survival group(7/8 vs. 14/29, χ 2=3.931, P=0.047). After CAR-T cell immunotherapy, the recovery period of CD19-positive cells in the death group, or the time for CAR-T cells to kill CD19-positive cells, was shorter than that in the survival group [42.00 days(30.00,49.00) vs. 55.00 days(41.50,73.50), Z=0.022, P=0.020]. Conclusion:The positive results of MRD by MFC at the following timepoints may predict unfavorable outcomes, such as post-CAR-T therapy and prior to transplantation, day 15 and 28 of the CAR-T cell immunotherapy, which may provide some guidance for clinical management.