Multiparametric Flow Cytometry for MRD Monitoring in Hematologic Malignancies: Clinical Applications and New Challenges

Abstract

Along with the evolution of immunophenotypic and molecular diagnostics, the assessment of Minimal Residual Disease (MRD) has progressively become a keystone in the clinical management of hematologic malignancies, enabling valuable post-therapy risk stratifications and guiding risk-adapted therapeutic approaches. However, specific prognostic values of MRD in different hematological settings, as well as its appropriate clinical uses (basically, when to measure it and how to deal with different MRD levels), still need further investigations, aiming to improve standardization and harmonization of MRD monitoring protocols and MRD-driven therapeutic strategies. Currently, MRD measurement in hematological neoplasms with bone marrow involvement is based on advanced highly sensitive methods, able to detect either specific genetic abnormalities (by PCR-based techniques and next-generation sequencing) or tumor-associated immunophenotypic profiles (by multiparametric flow cytometry, MFC). In this review, we focus on the growing clinical role for MFC-MRD diagnostics in hematological malignancies—from acute myeloid and lymphoblastic leukemias (AML, B-ALL and T-ALL), to chronic lymphocytic leukemia (CLL) and multiple myeloma (MM)—providing a comparative overview on technical aspects, clinical implications, advantages and pitfalls of MFC-MRD monitoring in different clinical settings.

Measurable residual disease in hairy cell leukemia: Technical considerations and clinical significance

“…An adequate BM or PB sample (1-2 ml) and an extensive antibody panel with backbone and lineage markers is needed is needed for MFC analysis of MRD. In addition, millions of clean CD45+ cell events should be acquired to ensure adequate LLOD and LLOQ levels ( 35 ). More recently, the International Group of Experts on Measurable Residual Disease in Hairy Cell Leukemia developed specific guidelines for evaluation of MRD in HCL (manuscript submitted).…”

The Role of T Cell Immunity in Monoclonal Gammopathy and Multiple Myeloma: From Immunopathogenesis to Novel Therapeutic Approaches

“…Consistent with this, the restoration of a functional anti-myeloma T cell immunity can represent an effective treatment option for advanced disease (as evidenced by CAR-T therapy in RRMM patients), and in turn, some immunological approaches could even be investigated at earlier stages (i.e., MGUS and SMM) to prevent the progression to symptomatic MM. In this view, the identification of novel specific T cell markers and the validation of significant T cell profiles may provide valuable new prognostic tools in the management of both MGUS and MM patients, possibly integrating with the emerging use of MRD, as assessed by next-generation sequencing and flow cytometry (NGS and NGF) [159]. In perspective, the prognostic monitoring of either spontaneous or therapyinduced anti-myeloma T cell responses, readily detectable in the PB or BM of MGUS/MM patients, may reasonably help guide the individualized use of adoptive T cell treatments in these settings.…”

Application of precision medicine in clinical routine in haematology—Challenges and opportunities

“…The choice of MRD markers and choice of tissue to examine often varies by type of malignancy and specific clinical needs. FC is widely used in most haematological malignancies [106] and measures protein markers at the surface of individual malignant cells and often a fresh bone marrow sample is required. Immunophenotypic evaluation by multiparameter FC can detect one malignant cell in 10 3 –10 5 normal cells [107], as it uses a combination of leukaemic specific markers.…”