Detection of minimal residual disease in patients with acute myeloid leukemia

Aim. Detection of minimal residual disease (MRD) in patients with acute myeloid leukemia (AML) and the study of its correlations with duration of recurrence-free interval. Material and methods. Bone marrow samples obtained from 37 AML patients before treatment were studied at two-color flow cytometry. The panel of monoclonal antibodies to T- and B-cell, myeloid antigens was used. The residual cells were estimated in 20 patients in remission. Results. 78% cases were diagnosed to have an anomalous immunophenotype including coexpression of lymphoid and myeloid antigens, asynchronous expression of myeloid antigens. In the first remission the residual cells were detected in 20 patients due to aberrant antigen expression. The presence of MRD was stated if bone marrow contained more than 0.12% leukemic cells. The duration of the first remission and MRD correlated: 8 patients with MRD had remission for 3 to 6 months (median 4.7 months). 12 patients free of MRD were in remission for more than 6 months (for 8 to 26 months, median 19.7 months). The threshold level of the residual cells (0.12%) was confirmed statistically using the three-parameter probability model. Conclusion. This study confirms feasibility of using flow cytometry for detection of residual cells. MRD and duration of the first remission correlate. Long-term observation of large groups of AML patients will try the validity of the above statistical model.