Allogeneic hematopoietic cell transplantation as the standard of care for blastic plasmacytoid dendritic cell neoplasm in first complete remission

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic disorder derived from precursors of plasmacytoid dendritic cells, with a generally aggressive clinical course. Tagraxofusp, a first-in-class CD123-directed antibody conjugate comprising human interleukin-3 and truncated diphtheria toxin, represents a welcome addition to the treatment armamentarium for BPDCN. Allogeneic hematopoietic cell transplantation (allo-HCT) is a treatment modality with curative potential in patients with BPDCN, based on data derived from registry studies, as well as multicenter and single-center retrospective studies. Several studies and a systematic review/meta-analysis have shown superior survival when patients undergo allo-HCT in first complete remission (CR1). In younger or fit patients, a myeloablative conditioning (MAC) allo-HCT regimen is the preferred approach whenever an allograft is indicated. Incorporating total body irradiation within the MAC regimen has been shown to improve progression-free survival, disease-free survival, and overall survival. However, MAC regimens have limited applicability in older, frail, or less fit patients, for whom reduced-intensity conditioning is the most appropriate approach. Several questions remain unanswered—namely, the potential benefit of post-transplant consolidation or maintenance strategies to mitigate the risk of relapse or progression, and the role of next-generation sequencing as a prognostic tool and for better defining depth of remission and measurable residual disease, among others. We believe that further improvement in the prognosis of BPDCN will require large collaborative efforts, considering the rarity of this disease.