Cumulative incidence of nonrelapse mortality by preparative regimen in patients with secondary MDS/tAML. High-dose TBI indicates high-dose TBI-containing regimens; BU/CY, busulfan and cyclophosphamide; tBU/CY, busulfan targeted to plasma levels of 600 to 900 ng/mL and cyclophosphamide; FLU/BU, busulfan targeted to plasma levels of 600 to 900 ng/mL and fludarabine; and FLU/TBI, fludarabine and TBI (200 cGy).