Rapid regression of bone marrow fibrosis after dose-reduced allogeneic stem cell transplantation in patients with primary myelofibrosis.

OBJECTIVE: To investigate the effect of a busulfan/fludarabine-based reduced intensity conditioning followed by allogeneic stem cell transplantation on regression of bone marrow fibrosis in patients with myelofibrosis. METHODS: Twenty-four patients (male, n = 16; female, n = 8) with a median age of 52 years (range, 32-63 years) were included. Six patients were transplanted from human leukocyte antigen-identical siblings and 18 patients from matched unrelated donors. Diagnosis was primary myelofibrosis in 18 patients and secondary myelofibrosis in 6 patients; in 4 of them, primary myelofibrosis evolved from polycythemia vera, and in 2 of them from essential thrombocythemia. Using the European Consensus on grading bone marrow fibrosis, all patients had advanced marrow fibrosis MF-2 (n = 13) or MF-3 (n = 11) before allografting According to the Lille Risk Factor Scoring System, patients were classified as low risk (n = 5), intermediate risk (n = 16), or high risk (n = 3). RESULTS: After stem cell transplantation, a complete (MF-0) or nearly complete (MF-1) regression of bone marrow fibrosis was seen in 59% at day +100, in 90% at day +180, and in 100% at day +360. No correlation between occurrence of acute graft-vs-host disease and fibrosis regression on day +180 was observed. CONCLUSION: This study shows that allogeneic stem cell transplantation after reduced-intensity conditioning resulted in rapid regression of bone-marrow fibrosis