Clinical Impact of [18F]FDG-PET/CT in ARI0002h Treatment, a CAR-T Against BCMA for Relapsed/refractory Multiple Myeloma

Multiple myeloma (MM) remains incurable, with poor outcomes in heavily pretreated patients. Chimeric antigen receptor (CAR) T-cell therapy has emerged as a promising treatment; however, outcomes after such therapy in patients with soft-tissue plasmacytomas and other bone lesions remain poorly understood. This study included 63 patients with relapsed/refractory MM treated either in the CARTBCMA-HCB-01 clinical trial (ARI0002h; academic B-cell maturation antigen [BCMA]-targeted CAR T-cell therapy) or in compassionate use. The aim was to evaluate the impact of soft-tissue involvement (extramedullary [EMD] and paraskeletal [PS] plasmacytomas) in response, survival and safety. Baseline [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) from 5 participating centers were reviewed centrally. Of 63 patients, 52.4% presented plasmacytomas at the time of inclusion (21 PS, exclusively; and 12 EMD). Per responses, there were no significant differences between patients with and without plasmacytomas. A correlation was present between International Myeloma Working Group responses and those obtained by [18F]FDG-PET/CT at day 100 (Bologna criteria). No differences were observed in progression-free survival (PFS) or overall survival (OS) between patients with or without plasmacytomas. However, both PFS and OS were significantly shorter in patients with EMD. Interestingly, [18F]FDG-PET/CT response assessed on day 100, in accordance with the Bologna criteria, was predictive of survival outcomes. A metabolic tumor volume of ≥25 cm3 at baseline [18F]FDG-PET/CT was associated with earlier disease progression and shorter OS. These results highlight the importance of EMD evaluation by [18F]FDG-PET/CT before and after CAR T-cell infusion. This trial was registered at www.ClinicalTrials.gov as #NCT04309981; and EudraCT, 2019-001472-11.