Multiparameter flow cytometry and ClonoSEQ correlation to evaluate precursor B-lymphoblastic leukemia measurable residual disease

Measurable residual disease (MRD) detection for precursor B-lymphoblastic leukemia (B-ALL) has become the standard of care. However, the testing methodology has not been standardized. We aim to correlate COG multiparameter flow cytometry (MFC) and ClonoSEQ techniques to assess the test characteristics, to study abnormal immunophenotype for B-ALL MRD, and to observe B-ALL clonal evolution and the impact of blinatumomab therapy on MFC testing. MFC and molecular reports were retrieved from electronic medical records and data was reviewed. Included in this study were 74 bone marrow samples collected from 31 B-ALL patients at our institution between January 2021 and March 2022. COG MFC and ClonoSEQ results were concordant in 59/74 samples (80%) with positive concordant results in 12 samples (16%) and negative concordant results in 47 samples (64%). Discordant results were seen in 15/74 samples (20%), with 14 samples (19%) showing ClonoSEQ + /MFC- results and only 1 sample (1%) showing MFC + /ClonoSEQ- result. ClonoSEQ + /MFC- cases had MRD values ranging from 1 to 1400 cells/million nucleated cells with 86% of cases showing MRD values of < 100 cells/million nucleated cells. Newly identified dominant sequences were detected using ClonoSEQ in 2/31 patients (6%) during follow-up. All 14 bone marrow samples from 8 patients, who had gone through blinatumomab immunotherapy, were MRD negative by MFC, but 3 cases were MRD positive by ClonoSEQ. Our results show strong correlation between COG MFC and ClonoSEQ (r = 0.96), and both methods are complementary. Clonal evolution may occur, and blinatumomab immunotherapy may impact MFC B-ALL MRD evaluation.