Phase II Study of Salvage Radiation Treatment After B-cell Maturation Antigen Chimeric Antigen Receptor T-cell Therapy for Relapsed Refractory Multiple Myeloma

This study is a Phase II study to determine the preliminary safety and efficacy of salvage radiation treatment after BCMA CAR-T therapy in subjects with RRMM. The study population will consist of subjects with RRMM previously treated with SOC BCMA CAR-T cell therapy with active disease on the D30+ PET or other imaging scan after CAR-T infusion. Patients who are planned for salvage chemotherapy less than 14 days after completion of radiation treatment will be excluded. Radiation treatment will be to bony or soft tissue plasmacytomas in up to five radiation treatment fields to 10-20Gy (or equivalent dose in 2Gy fractions of 10-21Gy). Final dose, target, and technique are per treating radiation physician discretion within these guidelines. Thirty patients will be enrolled. The co-primary endpoints are objective response rate (ORR) at 6 months and duration of response (DOR) among responders.