Cumulative incidence of relapse in children with ALL, according to levels of residual disease (RD) on flow cytometric assessment on day 19

. Levels of RD were defined by the percentage of mononuclear cells expressing leukemia-specific immunophenotypes; the solid line indicates 0.01% or more, and the broken line, less than 0.01%. (A) Patients 1 year of age or older in whom leukemic cells lacked the Ph chromosome. (B) Patients with less than 1% lymphoblasts on morphologic analysis on day 19. (C) Patients who had clinical remission and less than 0.01% MRD at the end of remission-induction therapy (day 46).