Stability of leukemia-associated aberrant immunophenotypes in patients with acute myeloid leukemia between diagnosis and relapse: comparison with cytomorphologic, cytogenetic, and molecular genetic findings.

Background: Multiparameter flow cytometry is increasingly used to monitor minimal residual disease in patients with acute myeloid leukemia to identify leukemic cells by leukemia-associated aberrant immunophenotypes (LAIPs). Changes in LAIPs during the course of the disease may be a limitation for this approach.

Methods: We analyzed 49 patients at diagnosis and relapse by flow cytometry, cytomorphology, cytogenetics, and molecular genetics.

Results: In 37 patients (76%), at least one LAIP detectable at diagnosis was present at relapse; in 12 patients (24%), none of the original LAIPs were present in at least 1% of bone marrow cells. Three groups were identified: no change in LAIPs, partial changes in LAIPs, and complete change in LAIPs. There were significant differences across these groups with regard to changes in cytomorphology (11%, 40%, and 58% of all cases, respectively; P = 0.007), cytogenetics (15%, 20%, and 25%; not significant), and molecular genetics (18%, 0, and 86%; P = 0.002).

Conclusions: These data indicate that, in a subset of patients with acute myeloid leukemia, the disease is biologically different at relapse; therefore, monitoring of minimal residual disease is difficult to accomplish. In most patients with acute myeloid leukemia, multiparameter flow cytometry may be used to monitor minimal residual disease.