Successful upfront cord blood transplantation for plasma cell leukemia in the first complete response after daratumumab therapy.

Plasma cell leukemia (PCL) is a rare and aggressive disease with a poor prognosis. Autologous or allogeneic stem cell transplantation (ASCT or allo-SCT) with intensive chemotherapy is performed for PCL, but their efficacy is still controversial. The efficacy of novel agents such as daratumumab for PCL is also unclear. Here, we report a case of PCL treated successfully with daratumumab and upfront cord blood transplantation (CBT) in the first complete response (CR). A 58-year-old man was diagnosed with PCL based on elevated abnormal plasma cells and IgD levels. After two cycles of bortezomib, lenalidomide, and dexamethasone therapy, some PCL cells remained in the bone marrow. We switched treatment to daratumumab, lenalidomide, and dexamethasone therapy and confirmed an immunophenotypic CR. We then performed CBT with fludarabine, melphalan, and total body irradiation for conditioning 3 months after diagnosis. Acute graft-versus-host disease was observed but controlled with corticosteroid therapy. The patient remained in stringent CR for 1 year after CBT. We successfully treated PCL with daratumumab followed by upfront CBT. Daratumumab was effective in PCL and could be used safely even before allo-SCT. Early use of daratumumab and early upfront allo-SCT may be a useful treatment option for PCL.