Clinical Impact of Minimal Residual Disease in Blood and Bone Marrow of Children with Acute Myeloid Leukemia.

The prognostic significance of bone marrow minimal residual disease (MRD) in pediatric patients with acute myeloid leukemia (AML) is well-characterized, but the impact of blood MRD is not known. We therefore used flow-cytometric assessment of leukemia-specific immunophenotypes to measure levels of MRD in both blood and bone marrow of patients treated on the AML08 (NCT00703820) clinical trial. Blood samples were obtained at days 8 and 22 of therapy, whereas bone marrow samples were obtained at day 22. Among patients who were MRD-negative in the bone marrow at day 22, neither day 8 nor day 22 blood MRD was significantly associated with outcome. However, day 8 blood MRD was highly predictive of outcome among patients who were bone marrow MRD-positive at day 22. Although the measurement of blood MRD at day 8 cannot be used to detect day 22 bone marrow MRD-negative patients who are likely to relapse, our findings suggest that day 8 blood MRD can identify bone marrow MRD-positive patients who have a dismal prognosis and who may be candidates for the early use of experimental therapy.