TEL/AML1 positivity in childhood ALL: average or better prognosis?

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.