Cumulative incidence of relapse in children with high-risk (A) and low-risk (B) ALL according to MRD studies at the end of remission induction.

Risk was defined by NCI criteria (see text for definition). All patients were in complete morphologic remission at the time of the MRD studies. MRD positivity is defined as ≥0.01% of mononuclear cells expressing leukemia-specific immunophenotypes.