METHODS
Among 7 patients with RP-mutated DBA who received HCT in Kyushu
University Hospital (n=6) and Kobe Children’s Hospital (n=1) from 2000
to 2020, the latest six patients received targeted BU and fludarabine
(FLU) conditioning in the first HCT. BU was administered intravenously
four times daily for four days. The cumulative area-under-the-curve
(AUC) of BU was calculated by JMP Pro 11 (version 11.2.0 for Windows;
JMP Inc., SAS Institute Japan) based on the results of a test-dose using
the Dried Blood Spot method. Based on the transfusion-dependent periods
and serum ferritin levels, the target of cumulative AUC was adjusted to
60–75 mg/L×h (65~80% of the conventional myeloablative
cumulative AUC [85–95 mg/L×h]). FLU was administered at 180
mg/m2 in four to six divided doses. Rabbit
anti-thymocyte globulin (rATG) (2.5–5.0 mg/kg
ThymoglobulinⓇ, Genzyme, Boston, MA) was added in five
patients. Tacrolimus and short-term methotrexate were used for acute
GVHD prophylaxis in all patients. The date of engraftment was defined as
the first of three consecutive days when the neutrophil count was
>0.5×109/L. Donor chimerism was assessed
by sex chromosome fluorescence in situ hybridization or short
tandem repeats.