Reduced intensity allogeneic stem cell transplantation for younger patients with myelofibrosis.

Allogeneic stem cell transplantation (alloSCT) is a curative procedure for myelofibrosis. Elderly people are mainly affected, limiting the feasibility of myeloablative regimens. The introduction of reduced-intensity conditioning (RIC) made alloSCT feasible for older patients. Nevertheless, the incidence of myelofibrosis is not negligible in young patients, who are theoretically able to tolerate high-intensity therapy. Very few data are available about the efficacy of RIC-alloSCT in younger myelofibrosis patients. This study included 56 transplanted patients aged <55 years. Only 30% had a human leucocyte antigen (HLA)-matched sibling donor, the others were transplanted from a fully-matched (36%) or partially-matched (34%) unrelated donor. All transplants were conditioned according the European Society for Blood and Marrow Transplantation protocol: busulfan-fludarabine + anti-thymocyte globulin, followed by ciclosporin and mycophenolate. One patient experienced primary graft failure. Incidence of graft-versus-host disease grade II-IV was 44% (grade III/IV 23%). One-year non-relapse mortality was 7% and the 5-year cumulative incidence of relapse was 19%. After a median follow-up of 8·6 years, the estimated 5-year progression-free survival and overall survival (OS) was 68% and 82%, respectively. Patients with fully-matched donor had a 5-year OS of 92%, in contrast to 68% for those with a mismatched donor (P = 0·03). The most important outcome-determining factor is donor HLA-matching. In conclusion, RIC-alloSCT ensures optimal engraftment and low relapse rate in younger myelofibrosis patients, enabling the possibility of cure in this group.