Negative CD19 Expression is Associated with Inferior Relapse‐free Survival in Children with RUNX1‐RUNX1T1–positive Acute Myeloid Leukaemia: Results from the Japanese Paediatric Leukaemia/Lymphoma Study Group AML‐05 Study

We performed a retrospective analysis of leukaemic surface antigen expression and genomic data from a total of 100 RUNX1-RUNX1T1-positive paediatric acute myeloid leukaemia (AML) patients enrolled in the Japanese Paediatric Leukaemia/Lymphoma Study Group (JPLSG) AML-05 protocol to determine risk factors for relapse. In univariate analysis, the KIT exon 17 mutation (n = 21) and CD19 negativity (n = 59) were significant risk factors for relapse (P = 0 center dot 01). In multivariate analysis, CD19 negativity was the sole significant risk factor for relapse (hazard ratio, 3 center dot 09; 95% confidence interval, 1 center dot 26-7 center dot 59; P < 0 center dot 01), suggesting that biological differences between CD19-positive and CD19-negative RUNX1-RUNX1T1 AML patients should be investigated.