Detection of residual disease in acute myeloid leukemia using light density gradients and culture assay.

For monitoring the effect of chemotherapy in acute myeloid leukemia (AML), we attempt to detect minimal numbers of AML clonogenic cells (CFU-L) during remission using light density gradients combined with PHA-LCM methyl cellulose assay. Fifteen patients in complete remission (CR) of AML were studied: 8 patients with Auer Rods (AR+), and 7 without Auer Rods (AR-). The cluster/colonies ratio and the granulocytic maturation of cells from pooled colonies were not significantly different whatever the density cut used (1077, 1062 or 1059). In all the AR+ patients, few AR+ cells (.06% +/- .03) were observed in bone marrow cultures during remission, without differences between density gradients, but not before plating. These AR+ cells were not found in culture of AR- patient bone marrows nor in normal marrows. The serial studies performed in 6 patients (4 AR+, 2 AR-) were not contributive for relapse prediction. In 2 cases, the second examination failed to detect AR+ cells: one was performed after an autologous bone marrow transplantation and the other in a patient with prolonged CR (54+ months). A quantitative analysis of residual CFU-L with our technique requires a cytological examination of each colony, that is very time consuming and limits its routine use.