Non-myeloablative conditioning for lower-risk myelodysplastic syndrome with bone marrow blasts less than 5 %-a feasibility study

Reduced-intensity conditioning (RIC) regimens can cause decreased non-relapse mortality (NRM) but lead to higher relapse rates in higher-risk myelodysplastic syndrome (MDS). However, relapse is not the main problem after hematopoietic cell transplantation (HCT) in lower-risk MDS, and post-transplant outcomes may therefore improve with less intense non-myeloablative conditioning (NMC) regimens. We here report the results of a single-center feasibility study of NMC with cyclophosphamide-fludarabine-antithymocyte globulin (CyFluATG) in MDS patients with bone marrow blasts < 5 %. We compared post-transplant outcomes between CyFluATG and a RIC regimen, busulfan-fludarabine-antithymocyte globulin (BuFluATG). Fifteen MDS patients received allogeneic HCT after CyFluATG conditioning comprising cyclophosphamide (100 mg/kg), fludarabine (150 mg/m(2)), and ATG, and 30 MDS historical control patients received BuFluATG conditioning which contained busulfan (8 [oral] or 6.4 [i.v.] mg/kg), fludarabine, and ATG. The 4-year overall survival (OS) and NRM rates were 80.0 and 20.0 % for CyFluATG and 73.3 and 20.0 % for BuFluATG, respectively. Neutrophil and platelet engraftment was significantly faster with CyFluATG than BuFluATG (median 12 vs. 14 days, P = 0.005 for neutrophils; median 15 vs. 21 days, P = 0.032 for platelets). CyFluATG produced a faster immune reconstitution of T-cells at 1 month after HCT than BuFluATG. Fertility was maintained after HCT with CyFluATG. In conclusion, the CyFluATG regimen is feasible in lower-risk MDS patients in terms of adequate engraftment and low NRM.