Avelumab in Combination With Hypofractionated Radiotherapy in Patients With Relapsed Refractory Multiple Myeloma

Background: Multiple myeloma is a cancer that forms from plasma cells which normally produce important immune response antibodies. It cannot be cured. Researchers hope the combination of radiation combined with the drug avelumab causes the immune system to kill myeloma cells more effectively. Objective: To see if avelumab given with radiation treatment helps treat multiple myeloma. Also to see if giving the treatments together is safe. Eligibility: People ages 18 and older with multiple myeloma that has come back after treatment and has spread to other parts of the body Design: Participants will be screened with: Medical history Physical exam Blood, urine, and heart tests Possible tumor biopsy Bone marrow testing: A needle will be stuck into the participants hipbone to take out a small amount of marrow. Positron emission tomography (PET)/Computed tomography (CT) scan and magnetic resonance imaging (MRI): Participants will lie in a machine that takes pictures of the body. Participants will get avelumab through an intravenous (IV). An IV is a small plastic tube put into an arm vein. They will get avelumab every 2 weeks for 2 doses. Then they will get radiation each day for 5 days. They will continue to get avelumab every 2 weeks as long as they do not have bad side effects and the treatment is helping their disease. Participants will have blood and urine tests, bone marrow biopsies, scans, and X-rays repeated during the study. Participants will have a follow-up visit 30 days after their last treatment dose. Then they will have visits every 3-6 months for up to 5 years....