Real-time immunophenotypic shifts in pediatric B lymphoblastic leukemia providing implications for minimal residual disease detection.

Objectives: Disease monitoring in acute leukemia management is crucial for risk stratification and chemotherapy response assessment. Minimal residual disease (MRD) testing is the most reliable tool, measuring antigenic expression differences between leukemic cells, hematogones, and mature benign B-cells. Modulation of antigen expression during treatment under chemotherapeutic drugs may complicate MRD analysis and detection. The present study investigates immunophenotypic modulation (IM) during chemotherapy phases in children with acute lymphoblastic leukemia (B-ALL), using a modified BFM protocol, and its potential implications for MRD detection.

Methods: The study was conducted at the Hematology Department, Indus Hospital and Health Network, Karachi. All MRD positive cases of pediatric B-ALL (1 month -16 years of age) were included, from April 2019- March 2022. MRD was done on bone marrow aspirate using 8-color flow cytometry. The data from 203 patients, who were MRD positive in bone marrow throughout the evaluation period was considered. The IM was assessed by comparative analysis of the changes in mean fluorescence intensity (MFI) of nine highly relevant antigens expressed by the leukemic cells.

Results: Statistically significant changes in the MFI levels of antigens were observed in leukemic blasts and mature benign B-cells. All the analyzed samples revealed IM to different extents. Our results confirm the presence of immunophenotypic changes for CD10, CD19, CD34, CD45, TdT, and CD66 during chemotherapy.

Conclusions: Measuring the MRD assists in monitoring the disease, however, IM of the different antigens expressed by the leukemic blasts should be considered and cautiously analyzed to prevent erroneous results.