Methodological aspects of diagnostics and minimal residual disease monitoring in infant acute leukemias

Hereby we present methodological aspects and prognostic significance of minimal residual disease (MRD) monitoring in infant acute leukemias. Based on our own experience we made algorithm for detection of MRD in this group of patients. We conclude that general concordance between MRD detection by flow cytometry and real-time polymerase chain reaction (PCR) for fusion gene transcripts achieved 87.0 %. Concordance was significantly lower during induction in comparison to consolidation/intensification and relapse treatment (78.6; 90.4 and 93.4 %, correspondingly; p = 0.002). It was not dependent on presence of normal B-cell precursors. Concordance between MRD results obtained by qualitative real-time PCR in bone marrow and peripheral blood samples was 84.5 %. Interestingly, all discrepant results (22 samples 15.5 %) were MRD-positive in bone marrow, but negative in peripheral blood. Despite high qualitative concordance rate between MRD detection in bone marrow and peripheral blood samples we could not show prognostic value of MRD monitoring in peripheral blood by fusion gene transcripts. Multivariate analysis revealed that MRD-positivity at time-point 4 in bone marrow was the only significant and independent prognostic factor of unfavorable outcome in the observed group of patients (hazard ratio 7.326; 95 % confidence interval 2.378–22.565).