Abstract 7 Reduced Intensity Conditioning Umbilical Cord Blood Transplantation in Combination with Splenic Irradiation in a Patient with Secondary Myelofibrosis and Massive Splenomegaly

INTRODUCTION: Myelofibrosis (MF) is a bone marrow neoplasm characterized by marrow fibrosis/failure and splenomegaly, causing pain, early satiety, and cytopenia. The only curative option is allogeneic hematopoietic stem cell transplant (allo-HSCT); however, its use is limited due to donor availability and patient age, functional status, and comorbidities. Umbilical cord blood (UCB) has been explored in this population for this reason with variable success, partly related to splenomegaly, which might influence engraftment in MF patients. OBJECTIVE: The objective was to report the successful use of UCB transplantation in conjunction with splenic irradiation to treat a patient with advanced MF and massive splenomegaly. METHODS: A 71-year-old male with post-essential thrombocythemia MF was treated with ruxolitinib for 2 years but developed worsening cytopenia and transfusion dependence. Splenomegaly (19.1×7.1×20.8 cm) was identified. Allo-HSCT was recommended on the basis of high-risk disease (DIPSS Plus score: 4) and few alternative options. Although suitable HLA-matched donors were unattainable, two cord blood units were available. A reduced intensity conditioning regimen of fludarabine, cyclophosphamide, and TBI 300 was chosen. Given the primary resistance to ruxolitinib, the spleen was irradiated with 450 cGy prior to transplant. RESULTS: Neutrophil and platelet engraftment occurred on days +30 and +49, respectively. The patient developed engraftment syndrome and acute graft versus host disease (GVHD) that resolved with methylprednisolone and early introduction of ruxolitinib. His immunosuppressive medications were discontinued by 6-months without evidence of chronic GVHD thereafter. He is now 1 year post-transplant with 100% donor chimerism and no clinical evidence of MF or GVHD. DISCUSSION: We present a novel therapeutic approach combining the use of splenic irradiation and a double unit UCB HSCT in a patient with MF and massive splenomegaly. UCB transplant should be considered in patients with MF who do not have an HLA-matched donor with the additional benefit of less chronic GvHD. Massive splenomegaly can negatively impact transplant outcomes due to entrapment of donor stem cells, delayed engraftment, and prolonged cytopenia. Splenic irradiation before UCB transplant can potentially reduce these complications, as it did in this case, and in turn decrease transplant-related mortality. Our future aim is to develop a clinical trial to study this approach.