Hematopoietic Cell Transplantation (HCT) Is an Effective Treatment for Blastic Plasmacytoid Dendritic Cell Neoplasm: Systematic Review and Meta-Analysis Assessing the Role of Allogeneic and Autologous HCT

Background: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare disease listed as a separate entity in the 5th edition of the World Health Organization Classification of Haematolymphoid Tumours. It is a clinically aggressive hematologic malignancy derived from precursors of plasmacytoid dendritic cells. Traditionally, therapeutic options for BPDCN consisted of conventional antineoplastic chemotherapy, adopted from regimens used to treat acute leukemia (myeloid or lymphoblastic, or lymphomas. Tagraxofusp, a CD123 directed antibody conjugate composed of human interleukin-3 (IL-3) and truncated diphtheria toxin, is also approved for treatment of BPDCN. Unfortunately, none of these are curative options of this disease. Allogeneic (Allo) hematopoietic cell transplantation (HCT) is an established treatment modality for patients with BPDCN with reported encouraging survival, whereas reported data on autologous (auto) HCT are limited.

Methods: We conducted a systematic review and meta-analysis (SR/MA) to assess the totality of evidence on the role of allo- and auto-HCT in patients with BPDCN. We performed a comprehensive search of EMBASE and PUBMED/MEDLINE, on April 25, 2024. To be eligible for inclusion in this SR/MA, studies must have included ≥10 patients; be published in full manuscript or letter to editor and have evaluated the use of an allo-HCT and/or auto-HCT for treating BPDCN. Pertaining to benefits, we extracted data based on complete remission (CR), progression-free survival (PFS) (substituted with disease-free survival (DFS) if PFS missing), and overall survival (OS). For harms, we extracted data on non-relapse mortality (NRM) and relapse. Data were pooled under a random effects model.

Results: Initial search identified 692 references, of which, 10 met our inclusion criteria. For allo-HCT, 10 studies were included; and for auto-HCT, there were 3 studies. For allo-HCT, pooled rates for CR, PFS/DFS and OS were 69% (2 studies, 91 patients (pts)), 49% (10 studies, 561 pts), and 55% (9 studies, 531 pts), respectively. Pooled rates for NRM and relapse were 24% (8 studies, 470 pts) and 24% (10 studies, 561 pts). Tests of heterogeneity were as follows: for CR analysis (I²=97.04%), PFS/DFS (I²=79.57%), OS (I²=33.18%), NRM (I²=0) and relapse (I²=55.55%). For auto-HCT, only one study reported CR=100%. Pooled rates of PFS/DFS and OS were 68% (3 studies, 43 pts), and 66% (3 studies, 43 pts), respectively. Pooled rates for NRM and relapse were 3% (2 studies, 27 pts) and 25% (3 studies, 43 pts). Tests of heterogeneity were as follows: for CR analysis (I²=not applicable), PFS/DFS (I²=0), OS (I²=27.90%), NRM (I²=0) and relapse (I²=0). A subgroup analysis for allo-HCT recipients in CR1 showed pooled rates of PFS and OS of 60% (5 studies, 76 pts) and 69% (5 studies, 76 pts), respectively. Tests of heterogeneity for PFS and OS for the allo-HCT in CR1 were I²=51.99% and I²=0, respectively.

Conclusion: Results of this SR/MA demonstrate that both allo-HCT and auto-HCT are effective treatments for patients with BPDCN, although data supporting the latter are scarce. Allo-HCT in CR1 is associated with a higher pooled rate of OS (69%). Efforts should focus on prompt referral of BPDCN patients for an allo-HCT in CR1, whenever possible, to optimize survival outcomes.

Murthy:Bristol Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees; Marker Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Senti Bioscience: Consultancy, Membership on an entity's Board of Directors or advisory committees; CRISPR therapeutics,: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees. Kharfan-Dabaja:Bristol Myers Squibb: Research Funding; Novartis: Research Funding; Kite Pharma: Honoraria; Pharmacyclics: Research Funding.