Investigation of the stem cell compartment in patients with chronic cytopenias and low-risk MDS

Abstract

Myelodysplastic syndromes (MDS) are defined by the WHO as a group of clonal haematopoietic stem cell (HSC) disorders which are characterised by cytopenias, ineffective haematopoiesis, dysplasia, the presence of blasts and an increased risk of developing Acute Myeloid Leukaemia (AML) (WHO,2022) Patients with persistent cytopenias are relatively frequent encounters in routine Haematology screening and the clinical management of these patients can be challenging due to unpredictable clinical course. This study aims to investigate the stem cell compartment of patients with persistent, unexplained cytopenias, and provide insights into the clinical behaviour of these conditions, aiding in better clinical management. In this study, the stem cell compartment of 53 patients was investigated in two separate cohorts: Cohort A (n=30) included patients with persistent cytopenias (potential pre-MDS conditions, or low-risk MDS) and Cohort B (n=23) patients with high-risk MDS and AML, as a control group. A one-tube flow cytometric assay was used for the detection of leukaemic stem cells (LSCs) using a combination of 13 different monoclonal antibodies, to identify immunophenotypic aberrancies. Molecular studies by next-generation sequencing (NGS) were carried out using a targeted myeloid NGS panel to detect any molecular aberrations. Immunophenotypic findings were then correlated with the molecular findings to confirm or otherwise the clonal nature of cytopenias. LSCs were found in 60% of patients from Cohort A and 91% of patients from Cohort B with the most common LSC markers being CD45RA and Combi markers. LSCs were detected at higher percentages in Cohort B. Various molecular aberrations which are commonly associated with MDS and AML were also detected in both Cohorts. There was high agreement between Immunophenotyping and Molecular results in Cohort A (56.6%) and Cohort B (91.3%). Cohort A was further sub-classified into low-risk MDS (50%), ICUS (33%), CCUS (7%) and ‘Other’ (10%) based on cytopenias, dysplasia and the presence of molecular aberrations. The presence of LSCs in 80% of LR-MDS patients, is an important adjunct finding that may prompt clinicians to monitor these patients more closely, with early therapeutic interventions in certain cases. In conclusion, patients with persistent cytopenias together with the presence of LSCs and molecular aberrations might have an increased risk of leukaemic progression and should be monitored more closely. The LSC assay provides valuable information on the stem cell compartment, better guiding clinicians on the course of action for patients with persistent cytopenias. Detection of LSCs is also important in view of the development of therapeutic targets such as immunotherapy targeted towards aberrant markers including CD33, CD123, TIM-3 and CLL-1 leading to more specific and personalised treatments (Hansen et al., 2022). Molecular analysis is also very important for patient stratification, prognosis and targeted therapy. The strong concordance between immunophenotyping and molecular results shows the importance of using a holistic approach when investigating patients with persistent cytopenia and suspected MDS.