Prognostic impact of early response to induction therapy as assessed by multiparameter flow cytometry in acute myeloid leukemia.

Objective: Early response after induction therapy is an independent prognostic factor in acute myeloid leukemia (AML). We improved the identification of this parameter by implementing multiparameter flow cytometry to quantify bone marrow cells carrying leukemia-associated immunophenotypes (LAIP).

Methods: In 106 uniformly treated patients flow cytometric analyses were performed at diagnosis and one week after induction therapy (day 16). The log-difference between LAIP-positive cells on day 1and day 16 (LD16) was determined for each patient.

Results: The LD16 (median, 2.11; range, -0.37 to 4.20) was significantly correlated to CR rate, event-free survival (EFS), overall survival (OS), and relapse-free survival (RFS). Separation of patients by the median LD16 resulted in significant differences in CR rate (81% vs. 51%, p=0.002), EFS (53% at 2 years vs. median 2.8 months, p<0.0001), 2-year OS (58% vs. 43%, p=0.0133), and 2-year RFS (65% vs. 30%, p=0.0037). Multivariate analysis revealed that LD16 was an independent prognostic parameter for CR rate, EFS, and RFS.

Conclusions: Flow cytometric evaluation of early response may serve as a new response parameter in AML. It may be used for development of risk-adapted therapies. High-risk patients can be identified early after the first induction therapy and assigned alternative and salvage treatment strategies.