Long-Term Survival of Patients with Myelofibrosis Treated with Allogeneic Hematopoietic Stem Cell Transplantation.

Myelofibrosis with myeloid metaplasia (MMM) is a disorder characterized by clonal myeloproliferation, ineffective erythropoiesis, extramedullary hematopoiesis and bone marrow fibrosis. Between 4/1998 and 1/2006, 17 patients with MMM were treated with allogeneic hematopoietic stem cell transplantation. Patients included 8 males and 9 females with a median age of 51.8 years (range 37–66). All patients were transfusion-dependent at the time of transplantation, 3 (18%) had abnormal cytogenetics and 4 (24%) had a prior splenectomy. Six patients (35%) received a reduced intensity conditioning regimen consisting of either fludarabine and busulfan (1 pt), fludarabine and low dose total body irradiation (1 pt), fludarabine and melphalan (3 pts) or fludarabine and cyclophosphamide (1 pt). Eleven patients (65%) received an ablative regimen of either busulfan and cyclophosphamide (10 pts) or cyclophosphamide and total body irradiation (1 pt). Patients with unrelated donors also received ATG as part of their conditioning. The hematopoietic cell source was peripheral blood in 12 pts (71%) and bone marrow in 5 pts (29%). Six pts (35%) received cells from an HLA-identical sibling, 1 pt (6%) had a 1 Antigen mismatch sibling and 10 pts (59%) received stem cells from an unrelated donor. Graft-versus-host disease prophylaxis consisted of tacrolimus in 15 pts (88%) and cyclosporine in 2 pts (12%).

Transplant-related mortality was 17% (sepsis 1 pt, VOD 1 pt, acute GVHD 1 pt) all occurring in the group treated with a myeloablative regimen. Of the remaining 14 patients, all achieved hematological recovery and transfusion independence. There were 2 relapses and one patient died of disease recurrence; both relapses occurred in the group receiving a reduced intensity regimen. The other 12 patients remain alive and in remission. The 6-year actuarial survival is 67% with no statistical difference between the groups who received a reduced intensity versus a myeloablative regimen.

In conclusion, Myelofibrosis with Myeloid Metaplasia can be successfully treated with allogeneic hematopoietic stem cell transplantation with a significant proportion of patients achieving long-term survival. Hematopoietic recovery can be achieved despite the presence of marrow fibrosis. The optimal preparative regimen remains to be determined with more relapses observed in the reduced intensity regimen group and a higher mortality seen in the myeloablative group. A risk-stratification strategy for regimen selection should be considered in future studies.