The presence of TEL/AML1 fusion gene in childhood acute lymphoblastic leuka
emia (ALL) defines a subgroup of patients with better than average outcome.
However, the prognostic significance of this aberration has recently been
disputed by the Berlin-Frankfurt-Munster (BFM) study group due to its relat
ively high incidence found in relapsed patients (19.6% and 21.9%, in two co
horts). In contrast, only four out of 45 (8.9%) unselected relapsed patient
s (all of whom had been treated according to BFM protocols) in the Czech Re
public carry this fusion. From March 1995 to June 1998, 41 out of 190 (21.6
%) newly diagnosed children with ALL were TEL/AML1-positive. There is a sta
tistically significant difference between the incidence of TEL/AML1 fusion
at diagnosis and at relapse within our group (P = 0.035). Interim analysis
of the minimal residual disease (MRD) detection shows heterogeneity within
the group of newly diagnosed TEL/AML1-positive leukaemias - 10 out of 24 pa
tients tested at the end of induction therapy had detectable levels of MRD.
However, only one of these patients reached relapse-predictive level (10(-
3)) of MRD. In conclusion, we corroborate low frequency of TEL/AML1 positiv
ity among relapsed patients with ALL among Czech children who are treated b
y the BFM: protocols. Moreover, we demonstrate different patterns of bone m
arrow clean-up in TEL/AML1-positive patients.