Sequential intrathoracic injection and intravenous infusion of BCMA CAR-T cells in a patient with relapsed/refractory primary plasma cell leukemia.

Patients with primary plasma cell leukemia (pPCL), particularly those with extramedullary disease (EMD), face a poor prognosis even with chimeric antigen receptor (CAR)-T cell therapy. This case report describes a patient with relapsed/refractory pPCL and life-threatening malignant pleural effusion (PE) treated with intrapleural CAR-T cells targeting B-cell maturation antigens. CAR-T cell expansion within the PE was observed, along with a rapid reduction in leukemia cell count and PE volume. Subsequent lymphodepletion chemotherapy and intravenous CAR-T cell therapy induced complete remission with 9 months of progression-free survival. This case highlights the potential advantages of integrating local and systemic CAR-T cell therapy in managing complex EMD cases.