This phase III trial studies how well lenalidomide and dexamethasone works with or without daratumumab in treating patients with high-risk smoldering myeloma. Drugs used in chemotherapy, such as lenalidomide and dexamethasone, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Immunotherapy with monoclonal antibodies, such as daratumumab, may induce changes in the body's immune system and may interfere with the ability of tumor cells to grow and spread. Giving lenalidomide and dexamethasone with daratumumab may work better in treating patients with smoldering myeloma.

This phase II trial tests daratumumab given at a reduced frequency with lenalidomide for maintenance therapy for the cost effective treatment of patients with multiple myeloma post stem cell transplant. Darzalex Faspor (also known as Daratumumab-hyaluronidase) is a combination of two drugs used alone or with other drugs to treat adults with certain types of multiple myeloma or light chain amyloidosis. Daratumumab binds to a protein called CD38, which is found on some types of immune cells and cancer cells, including myeloma cells. Daratumumab may block CD38 and help the immune system kill cancer cells. Hyaluronidase allows daratumumab to be given by injection under the skin. Daratumumab and hyaluronidase can be given in less time than daratumumab alone, which is given as an infusion. Lenalidomide may stop or slow cancer cells by blocking the growth of new blood vessels necessary for tumor growth. Daratumumab-hyaluronidase is typically given every 4 weeks per standard of care. Giving it every 8 weeks for the first year followed by every 16 weeks for years 2 through 4 in combination with lenalidomide may be equally as effective and reduce costs and treatment visits for patients with multiple myeloma post stem cell transplant.