Daratumumab for Relapsed/Refractory Primary Effusion Lymphoma, Plasmablastic Lymphoma, and Multicentric Castleman Disease

Background: Primary effusion lymphoma (PEL), plasmablastic lymphoma (PBL), and Multicentric Castleman Disease (MCD) are aggressive forms of cancer that affects cells in the immune system and lymph nodes. How they develop is not well understood, and these diseases do not respond well to standard treatments for other types of lymphomas. Objective: To test a drug treatment (daratumumab SC) in people with PEL, PBL, or MCD. Eligibility: People aged 18 and older with PEL, PBL, or MCD who must have failed to respond to therapy or they must be unable to receive standard treatment for the disease. Design: Participants will be screened. They will have a physical exam with blood tests. They will have imaging scans and tests of their heart and lung function. They may need to have a biopsy: tissue or fluid will be collected. They will have an eye exam. Daratumumab SC is given as an injection into the fat under the skin in the abdomen. This takes 3 to 5 minutes. Participants will receive the treatment once a week for 8 weeks; then every 2 weeks for 16 weeks; then every 4 weeks for up to 24 months. Participants will have other tests during the study period. These may include lumbar punctures: A needle will be inserted between the bones of the spine to draw some fluid from the area around the spinal cord. Participants may also have a thoracentesis: A needle or plastic tube will be inserted into the space around the lungs to withdraw fluid. Participants will have more imaging scans and blood tests. Follow-up visits will continue after treatment ends. Participants will be in the study for up to 5 years.