Reduced-intensity conditioning versus myeloablative conditioning allogeneic stem cell transplantation for patients with myelofibrosis.

Background
Allogeneic hematopoietic stem cell transplantation (alloSCT) is the sole curative option for myelofibrosis (MF). However, it is unknown as to which of the two, myeloablative conditioning (MAC) or reduced-intensity conditioning (RIC), is a better preconditioning regimen.


Methods
Twenty-five patients with MF were treated with alloSCT, 12 of whom underwent RIC. Baseline characteristics, response to alloSCT, adverse events, including graft-versus-host disease (GVHD), and survival outcomes were reviewed.


Results
There was no difference in the neutrophil engraftment rate and time to engraftment between MAC vs. RIC. The time to platelet engraftment was significantly longer in the MAC group (median, 112.8 vs. 28.8 days for MAC vs. RIC, respectively, P=0.049). RIC was more advantageous in terms of achieving complete chimerism (38.5% vs. 83.3%, P=0.041). The incidence of acute GVHD was 84.6% (11 of 13) and 58.3% (7 of 12) in the MAC and RIC groups, respectively. The cumulative incidence of grade III-IV acute GVHD was significantly higher in the MAC group than in the RIC group (P=0.03). No significant differences were observed in progression-free and overall survival. The 17-month probability of progression-free survival was 38.4% [95% confidence interval (CI), 19.3-76.5] vs. 47.6% (95% CI, 25.7-88.2) (P=0.21), and that of overall survival was 53.8% (95% CI, 32.5-89.1) vs. 48.6% (95% CI, 26.8-88.3) (P=0.85) for MAC vs. RIC, respectively.


Conclusion
RIC offers a significant advantage over MAC, even in younger patients with MF undergoing alloSCT, in terms of cell engraftment, rate of complete chimerism achievement, and incidence of acute GVHD.