Tumor burden is similar at MDS and secondary AML. Tumor burden at MDS and secondary AML (percentage of bone marrow cells) from 8 patients assessed at both time points.^17,18  Tumor burden was measured by morphology using the blast count percentage and sequencing of total bone marrow cells (ie, percentage of clonal cells based on the mutations’ variant allele frequency). Although the blast count increases significantly from MDS to secondary AML, the percentage of clonal cells based on sequencing is similar at both time points. Data are mean ± standard deviation.