Abstract

Background: MRD measurement is based on the ability to detect a minimal quantity of tumor cells within a population of healthy cells. Given the low sensitivity of cytology, flow cytometry in T-ALL allows the distinction between normal cells and leukemic cells and classifies patients according to their prognosis. The aim of this study was to define the immunophenotypic features of T-ALL at different stages of differentiation in terms of minimal residual disease.
Methods: This is a prospective study carried out in the Hematology Laboratory of the IBN ROCHD University Hospital in Casablanca Morocco over a period of 3 years and 4 months from September 1, 2020, to December 31, 2023. All patients were included. Pediatric ALL patients, ranging from 1 month- to 15-years old, whose cytological bone marrow remission was confirmed by myelogram at the different phases of treatment: end of induction and end of consolidation, were diagnosed according to the EGIL and WHO - HAEM classifications and followed up in the Pediatric Oncohematology Department. Immunophenotyping was carried out by a Navios Beck Man Coulter 6-color cytometer and 2 lasers equipped with CXP software on bone marrow samples with a panel of 3 tubes: 1-CD5CD7CD3CD10CD3s CD45/2-CD4CD8CD99CD3sCD10CD45/3-CD2CD1CD99CD3CD10CD45; thus, the technical validation consisted of the adjustment of the PMT, determination of the optimal concentrations of the antibodies, establishing the AC panel on normal marrows, the study of the sensitivity and linearity of the technique, and the evaluation of the representativeness of the samples by calculating hemodilution according to Brooimans law.
Results: Twenty-five patients were found to be in complete cytological remission, and the analysis of minimum residual disease (MRD) post-induction showed a significant difference (p = 0.0020). Among those with MRD levels less than 10 - 3, none were ETP (0.0%), while 3 (25.0%) were near-ETP and 9 (75.0%) were non-ETP, totaling 12 patients. For those with MRD levels above or equal to 10 - 3, 8 (61.5%) were ETP, 3 (23.1%) were near-ETP, and 2 (15.4%) were non-ETP, totaling 13 patients. Similarly, MRD levels post-consolidation also indicate a significant difference (p = 0.0020), mirroring the results from the post-induction analysis.
Conclusions: Our study panel was close to that proposed by a Brazilian study by Roshal et al. [43] and the American study by Wood et al. [44] and was the first large one that describes the immunophenotypic profile of minimal residual disease in T-ALL patients. We concluded that cytometry proves to be a good complement to molecular biology, because it makes it possible to monitor patients who do not have molecular biology monitoring markers. Its limit remains a lower sensitivity than that obtained with molecular biology. If a sensitivity of 10 - 3 is desired, CMF is sufficient for MRD.

DOI: 10.7754/Clin.Lab.2025.250120