Predictive values of baseline 18F-FDG PET/CT for toxicities and outcomes in patients with relapsed or refractory multiple myeloma following BCMA CAR T-cell therapy.

Patients with relapsed/refractory multiple myeloma (R/R MM) receiving chimeric antigen receptor (CAR) T-cell therapy are at high risk of toxicities, including cytokine release syndrome (CRS). The roles of positron emission-tomography computed tomography (PET/CT) in predicting these toxicities remain unclear. We retrospectively studied 62 patients with R/R MM who received B-cell maturation antigen (BCMA) CAR T-cell therapy at our center. Baseline metabolic tumor volume (MTV) of more than 107.2 cm3 and total lesion glycolysis (TLG) exceeding 406.5 were classified as high MTV and high TLG, respectively. Both high MTV (P = 0.008) and high TLG (P = 0.011) were identified as independent risk factors for the development of severe CRS classified as grade 3 to 4. Moreover, the administration of tocilizumab for the treatment of CRS was associated with high MTV (P = 0.005) or high TLG (P = 0.010). Notably, our multivariate Cox models that incorporated either MTV (P = 0.029) or TLG (P = 0.009) along with plasmacytoma types, high-risk cytogenetics, and high bone marrow plasma cell frequencies demonstrated strong predictive capabilities for the 5.3-year long-term OS. Therefore, baseline high MTV or TLG measured by PET/CT are recognized as adverse prognostic indicators for the incidence of severe CRS and poor outcomes in patients with R/R MM undergoing BCMA CAR T-cell therapy.