To study the outcomes of allo-HCT in patients with hematological malignancy who received BU3 (9.6 mg/kg) based conditioning from matched related or unrelated donors.

A retrospective analysis of KFSHRC- BMT Database, we identified 65 patients who received Allo-HCT between October 2005 and December 2019 at King Faisal Specialist Hospital & Research Center. The patients received SCT from full HLA matched related or unrelated donors. We excluded Mismatched MUD, Cord & Haplo-identical Stem Cell sources.

We identified 47 AML (72.3%), 8 MDS (12.3%), 8 Myelofibrosis (12.3%) & 2 CML (3.1%) patients. Acute GvHD grade II-IV and III-IV occurred in 29% and 14% respectively. Chronic GvHD occurred in 55% and was extensive in 24% of patients. With Median follow-up 60.5 months, 2 years and 5 years OS were 58.5 % and 44.1% respectively. The 2 years and 5 years DFS were 52.9% and 44.5% respectively. Cumulative incidence of relapse and NRM at 2- years were 29.5% and 17.4% respectively. Day +100 TRM were 10.7%

Allogeneic SCT using BU3 based regimen appears feasible to use in patients who are not suitable for fully myeloablative (BU4) regimen. TRM, DFS & OS rate were comparable to reports from studies using BU4 based regimen, warranting prospective studies in these patients.