Australasian Trends in Allogeneic Stem Cell Transplantation for Myelofibrosis in the Molecular Era: A Retrospective Analysis from the Australasian Bone Marrow Transplant Recipient Registry

To review the updated trends of national practice and outcomes in transplantation to treat myelofibrosis (MF), we retrospectively evaluated 142 patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) for primary (n = 94) or secondary (n = 48) MF at an Australian/New Zealand transplantation center between 2006 and 2017. The median duration of follow-up was 51.8 months (range, 3.1 to 148 months). The median age at allo-HSCT was 56 years (range, 26 to 69 years). Fifty-two percent of the patients had HLA-identical sibling donors, and 45% had matched unrelated donors (UD). Conditioning regimens were predominantly reduced intensity (83%). Before transplantation, 16% of the patients had undergone splenectomy or splenic irradiation, and 38% (n = 54) received JAK inhibitor therapy. JAK2 mutation testing was performed in 66.9% of the patients, whereas other mutations (CALR, MPL, ASXL1, SRSF2, U2AF1Q57, EZH2, and IDH1/2) were rarely tested (1.4% to 8.4%). Only 4.2% of patients had next-generation sequencing mutation analysis. The median time to neutrophil engraftment was 19 days (range, 10 to 43 days), and the median time to platelet engraftment was 27 days (range, 13 to 230 days). The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 21.4% at 100 days, and that of extensive chronic GVHD (cGVHD) at 5 years was 18.1%. Overall survival (OS) was 67% at 1 year and 57% at 5 years. GVHD-free, relapse-free survival was 54% at 1 year and 42% at 5 years. The cumulative incidence of nonrelapse mortality (NRM) was 16% at 100 days and 25% at 1 year. In multivariate analysis, age ≥65 years and use of an UD were identified as significant unfavorable risk factors for OS and NRM. Use of an UD increased the incidence of aGVHD, whereas administration of antithymocyte globulin/alemtuzumab lowered the risk of both aGVHD and cGVHD. Pretransplantation splenectomy/splenic irradiation had a positive influence on time to engraftment. There have been no improvements in the outcomes of allo-HSCT for MF in Australasia over the last decade, with a low uptake of molecular genomic technology due to limited access to funding.