The definition of remission in acute leukemia with immunologic techniques

In acute leukemia residual disease is usually monitored by morphology. The precision of this approach can be improved by several methods including the investigation of chromosomal abnormalities by conventional cytogenetics, flow karyotyping, in situ hybridization and polymerase chain reaction (PCR), and the analysis of immunoglobulin and T cell receptor genes by Southern blotting and PCR. Immunologic methods represent a reliable option for studying residual disease in approximately half of the patients with acute leukemia. This strategy is based on the observation that some marker combinations are expressed on leukemic blasts but are absent or rarely present in normal peripheral blood (PB), bone marrow (BM) or cerebrospinal fluid cells. In patients with T cell-acute lymphoblastic leukemia, even one cell simultaneously expressing terminal deoxynucleotidyl transferase and CD3, CD5 or CD1 amongst 10(5) PB or BM cells indicates residual disease. Some cases of B lineage and myeloid acute leukemias also exhibit phenotypes potentially useful for monitoring response to treatment. Such phenotypes are identified by double or triple color staining techniques using fluorescence microscopy or flow cytometry. Independent studies have demonstrated that detection of cells with leukemia-associated phenotypes in BM samples of patients in clinic and morphologic remission heralds the recurrence of leukemia. It is likely that a combination of techniques will be needed to monitor the majority of patients with acute leukemia. Advantages and disadvantages of individual methods should be determined in comparative preclinic investigations. These studies should yield sufficient information to initiate the testing of therapeutic strategies planned according to the data provided by use of modern sensitive techniques.