Patient Characteristics and Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Abstract

Background: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy arising from plasmacytoid dendritic cells. It commonly presents as skin lesions with or without bone marrow, lymph node, central nervous system (CNS), or systemic involvement. Limited retrospective data have shown durable remissions after allogeneic (allo) hematopoietic cell transplantation (HCT). Methods: In this retrospective single-center analysis, we evaluated outcomes of 31 BPDCN patients treated with allo-HCT between September 2000 and June 2023 at our institution. Results: Median age of our cohort was 52 years [range 16-76 y]. Patient characteristics are summarized in the attached Table. Only 6 patients (19%) had their disease confined to skin and 4 (13%) had CNS/CSF involvement at diagnosis. Four patients (13%) had prior hematologic malignancies (HM), and 9 patients (29%) had a cytogenetic abnormality at baseline. Thirteen (42%) patients, who were evaluated by a next-generation sequencing Leukemia Mutation Panel, had TET2 mutation. Median time from diagnosis to HCT was 6.2 (3.2-42.4) months. Eight (26%) patients received tagraxofusp, matched unrelated donor was the most common donor type (39%), and fludarabine + busulfan-based conditioning was used in 17 (55%) patients. Post-transplant cyclophosphamide (PTCy) was used for GVHD prophylaxis in 23 (74%) patients. Median follow up was 23.9 (0.9-119.9) months. One-hundred day and 1-year non-relapse mortality was 9.7% and 23.1%, respectively. Grade 2 acute GVHD was seen in 9 patients (29%), and no grade 3-4 GVHD has been seen so far. Limited or extensive chronic GVHD was seen in 6 (21%) of 28 evaluable patients. Only 6 of the 31 (19%) allo-HCT patients progressed after HCT. Two-year PFS and OS was 56% and 67%, respectively. Patients receiving allo-HCT in first remission had significantly better median PFS (not reached vs. 11.3 months; p=0.034) and OS (not reached vs. 12.6 months; p=0.045). Conclusions: These results demonstrate the safety and efficacy of allo-HCT in BPDCN. Patients undergoing allo-HCT in first remission had significantly better outcomes. Prospective studies are needed to better define the role of allo-HCT in BPDCN.