KMT2A and acute lymphoblastic leukemia: To examine the extent to which ctDNA reflects MLL-r ALL burden in MRD sites, plasma ctDNA concentrations were compared to BM MRD as well as the % huCD45+ cells in the spleen and in cardiac puncture blood collected from euthanized mice at Day 0, 14, and 28 and at 1% huCD45+ or endpoint (Figure 5).