Minimal residual disease studies by flow cytometry in acute leukemia

Minimal residual disease (MRD) assays are increasingly important in the clinical management of patients with acute leukemia. Among the methods available for monitoring MRD, flow cytometry holds great promise for clinical application because of its simplicity and wide availability. Several studies have demonstrated strong correlations between MRD levels by flow cytometry during clinical remission and treatment outcome, lending support to the reliability of this approach. Flow-cytometric detection of MRD is based on the identification of immunophenotypic combinations expressed on leukemic cells but not on normal hematopoietic cells. Its sensitivity depends on the specificity of the immunophenotypes used to track leukemic cells and on the number of cells available for study. Immunophenotypes that allow detection of 1 leukemic cell in 10,000 normal cells can be identified in at least 90% of patients with acute lymphoblastic leukemia; immunophenotypes that allow detection of 1 leukemic cell in 1,000-10,000 normal cells can be identified in at least 85% of patients with acute myeloid leukemia. Identification of new markers of leukemia by gene array technology should lead to the design of simple and reliable antibody panels for universal monitoring of MRD. Here we review the relative advantages and disadvantages of flow cytometry for MRD studies, as well as results obtained in correlative studies with treatment outcome.

Towards an integrated classification of adult acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) represents a biologically and clinically heterogeneous group of diseases characterized by the abnormal proliferation and accumulation of immature lymphoid cells within the bone marrow and lymphoid tissues. Following a diagnostic work-up, prognostic data are routinely achieved through physical examination, serum biochemical profiles, peripheral blood count and bone marrow morphology. Over the years, information obtained through karyotype, molecular genetics, extensive immunophenotype, multidrug resistance and, more recently, genomic profiling is progressively contributing to a better understanding of the biology of this complex disease, to the identification of subgroups of patients with a different clinical outcome, to the more precise monitoring of minimal residual disease, to the use of different therapeutic protocols based on prognostic indicators and, recently, also to the design of innovative and specific treatment strategies. In the present review, we will discuss how an integrated approach is now mandatory for the optimal management of adult ALL.