SCIENTIFIC PROGRAMME
SESSION I
BIOLOGY OF B-CELL
PRECURSOR ALL
SESSION II
BIOLOGY OF T-CELL ALL
SESSION III
MINIMAL RESIDUAL
DISEASE MONITORING
SESSION IV
INDIVIDUALIZED
MANAGEMENT OF ALL
SESSION V
NEW ADVANCES IN ALL
SESSION VI
CAR T-CELLS &
ALLOGENEIC HSCT
SESSION VII
FRONTLINE
INCORPORATION OF
BITES AND ADCS
SESSION VIII
T-CELL ALL AND
LYMPHOBLASTIC
LYMPHOMA
SESSION IX
PH AND PH-LIKE ALL
SELECTED ABSTRACTS
FOR AN ORAL
PRESENTATION
SELECTED ABSTRACTS
AS E-POSTERS
DISCLOSURES
ESTER MEJSTRIKOVA (PRAGUE)
MYELOID SWITCH OF B-CELL PRECURSOR ALL SUBTYPES
We described B-cell precursor acute lymphoblastic leukemia (BCP-ALL) subtype with early switch to
the monocytic lineage and loss of the B-cell immunophenotype, including CD19 expression. Among
726 children consecutively diagnosed with BCP-ALL, 8% patients experienced switch detectable by flow
cytometry (FC). Using exome and RNA sequencing, switch was found to positively correlate with three
different genetic subtypes: PAX5-P80R mutation (5 cases with switch out of 5), rearranged DUX4
(DUX4r; 30 cases of 41) and rearranged ZNF384 (ZNF384r; 4 cases of 10). If switching was not taken
into account, the B-cell-oriented FC assessment underestimated the minimal residual disease level. For
patients with PAX5-P80R, a discordance between FC-determined and PCR-determined MRD was found
already on day 15, resulting from a rapid loss of the B-cell phenotype. Discordance on day 33 was
observed in all the DUX4r, PAX5-P80R and ZNF384r subtypes. Importantly, despite the substantial
phenotypic changes, possibly even challenging the appropriateness of BCP-ALL therapy, the monocytic
switch was not associated with a higher incidence of relapse and poorer prognosis in patients
undergoing standard ALL treatment. Currently therapies targeting CD19 antigens are introduced into
relapsed and frontline protocols and the knowledge about the switch to monocytic lineage is of
importance for evaluation of the effectivity of these therapies.