Summary Blinatumomab with subsequent haematopoietic stem cell transplantation was applied in 13 infants with acute lymphoblastic leukaemia (ALL). Eight patients were treated in first remission due to slow clearance of minimal residual disease (MRD); one for MRD‐reappearance after long MRD negativity, one for primary refractory disease and three during relapse treatment. In slow MRD responders, complete MRD response was achieved prior to transplantation, with an 18‐month event‐free survival of 75%. In contrast, only one of five patients with relapsed/refractory ALL is still in complete remission. These data provide a basis for future studies of immunotherapy in very high‐risk infant ALL.

Summary This study aimed to evaluate the concordance between minimal residual disease (MRD) results obtained by multicolour flow cytometry (MFC) and polymerase chain reaction for fusion gene transcripts (FGTs) in infants with acute lymphoblastic leukaemia (ALL) associated with rearrangement of the KMT2A gene (KMT2A‐r). A total of 942 bone marrow (BM) samples from 123 infants were studied for MFC‐MRD and FGT‐MRD. In total, 383 samples (40.7%) were concordantly MRD‐negative. MRD was detected by the two methods in 441 cases (46.8%); 99 samples (10.5%) were only FGT‐MRD‐positive and 19 (2.0%) were only MFC‐MRD‐positive. A final concordance rate of 87.4% was established. Most discordance occurred if residual leukaemia was present at levels close to the sensitivity limits. Neither the type of KMT2A fusion nor a new type of treatment hampering MFC methodology had an influence on the concordance rate. The prognostic value of MFC‐MRD and FGT‐MRD differed. MFC‐MRD was able to identify a rapid response at early time‐points, whereas FGT‐MRD was a reliable relapse predictor at later treatment stages. Additionally, the most precise risk definition was obtained when combining the two methods. Because of the high comparability in results, these two rather simple and inexpensive approaches could be good options of high clinical value.

Aim:The aim of the study was to evaluate the incidence and prognostic impact of central nervous system (CNS) involvement in infants with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), as well as its relation with minimal residual disease (MRD) data.Methods: A total of 139 consecutive infants with BCP-ALL from the MLL-Baby trial were studied. Cerebrospinal fluid (CSF) samples were investigated by microscopy of cytospin slides. MRD was evaluated according to the protocol schedule by flow cytometry and PCR for fusion gene transcripts (FGT).