[HLA-haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide in patients with...

Allogeneic hematopoietic stem cell transplantation is the only curative treatment for myelofibrosis. However, the high risk of non-relapse mortality and the difficulty of finding an HLA-matched sibling donor are obstacles, given the advanced age at disease onset. Here, we report four cases of transplantation from an HLA-haploidentical donor using post-transplant cyclophosphamide (PTCy-haplo) in three recipients with primary (n=1) and secondary (n=2) myelofibrosis. The median age was 52 years, and one patient had received JAK2 inhibitor therapy prior to transplantation. The sources were bone marrow and peripheral blood stem cells (two cases each); myeloablative conditioning was used in two cases. Neutrophil engraftment was achieved in all cases (median 19 days); however, prolonged G-CSF administration (median 44 days) was required, and platelet engraftment was delayed (median 68 days). Two patients survived without relapse, with observation periods of 3.5 and 8 years, respectively. One patient relapsed 17 months after the first transplantation and died of pneumonia 49 days after second PTCy-haplo. These findings suggest that PTCy-haplo is a feasible option for patients with myelofibrosis; however, the risk of delayed hematopoietic recovery should be noted.