Outcome after Transplantation According to Reduced-Intensity Conditioning Regimen in Patients Undergoing Transplantation for Myelofibrosis

Allogeneic hematopoietic stem cell transplantation remains the sole curative option for myelofibrosis. Many transplantation recipients receive a reduced-intensity conditioning (RIC) regimen owing to age or comorbidities; however, there is little published evidence to guide the choice of RIC regimen. In this study, we compared outcomes in patients who received 1 of 2 frequently used RIC regimens for patients with myelofibrosis: fludarabine-busulfan (FB) and fludarabine-melphalan (FM). A total of 160 patients underwent a RIC allograft procedure (FB group, n = 105; FM group, n = 55). We have developed a complex statistical model involving weighting and adjustment to permit comparison between these 2 groups. After weighting, the incidence of acute graft-versus-host disease (GVHD) was 62% in the FM group and 31% in the FB group (P = .001), and the corresponding incidence of chronic GVHD was 49% and 53%, respectively. The 7-year progression-free survival was were 52% in the FM group versus 33% in the FB group, and the 7-year overall survival rate 52% in the FM group versus 59% in the FB group. Nonrelapse mortality (NRM) was 43% in the FM group and 31% in the FB group. Multivariable analyses revealed no significant differences in PFS between the 2 groups; however, the relapse rate was significantly lower in the FM group (hazard ratio, 9.21; P = .008), whereas a trend toward reduced NRM was seen in the FB group (hazard ratio, 0.51; P = .068). In conclusion, both regimens appear to be efficient in mediating disease control and can be used to successfully condition patients with myelofibrosis. The FM regimen appears to induce more NRM than the FB regimen, but with augmented control of disease, leading to comparable overall survival rates for both regimens.