[Successful treatment of myelomatous pleural effusion with daratumumab administration before autologous peripheral stem cell transplantation].

A 50-year-old woman diagnosed with surgically resected plasmacytoma of the ovaries and uterus presented with another plasmacytoma in the pancreas with positive uptake on positron emission tomography (PET) and massive right pleural effusion with plasma cell infiltration (myelomatous pleural effusion). After four courses of the bortezomib, lenalidomide, and dexamethasone regimen as induction therapy, partial response was achieved with reduced myelomatous pleural effusion and negative uptake on PET in the pancreatic plasmacytoma. However, soon after she received bortezomib and high-dose cyclophosphamide for peripheral blood stem cell harvesting, right myelomatous pleural effusion increased without signs of heart failure or infection. Because of the progressive nature of the disease, daratumumab was introduced as 2 courses of daratumumab, lenalidomide, and dexamethasone (DLd) regimen, after which she achieved complete response with disappearance of the pleural effusion. After autologous peripheral blood stem cell transplantation, she received an additional four courses of the DLd regimen as consolidation therapy. She maintained relapse-free survival for two years with maintenance therapy containing daratumumab and dose-reduced lenalidomide. Our case may suggest the usefulness of daratumumab before autologous peripheral stem cell transplantation for relapsed/refractory myelomatous pleural effusion.