Allogeneic hematopoietic cell transplantation for myelofibrosis using fludarabine-, intravenous busulfan- and low-dose TBI-based conditioning.

Graft failure is one of the major barriers to the success of allogeneic hematopoietic cell transplantation (HCT) in myelofibrosis (MF). We report our institutional experience with 27 MF patients who underwent HCT using fludarabine-, intravenous BU- and low-dose total body irradiation (FBT)-based reduced-intensity (n=20) or full-intensity (n=7) conditioning regimens. Eight patients had prior exposure to JAK1/2 inhibitor therapy; six patients received JAK1/2 inhibitors leading on to HCT and two patients received transplant at the failure of JAK1/2 inhibitor therapy. No adverse impact of JAK1/2 inhibitor therapy was observed on early post-transplant outcomes. All evaluable patients had neutrophil recovery, and no primary graft failure was observed. Cumulative incidence of grades II-IV acute GVHD at day 100 was 48% (95% confidence interval (CI), 29-67%) and chronic GVHD at 2 years was 66% (95% CI, 49-84%). Cumulative incidences of nonrelapse mortality (NRM), relapse and probability of OS at 2 years were: 43% (95% CI, 12-74%), 10% (95% CI, 0-39%) and 56% (95% CI, 28-77%), respectively. FBT-based conditioning regimen has a favorable impact on engraftment; however, further efforts are required to reduce NRM.