Prognostic implications of splenomegaly in BCMA-directed CAR T-Cell therapy for relapsed myeloma

B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T-cell therapy has shown promise for patients with relapsed or refractory multiple myeloma (RRMM), yet its use is often complicated by adverse events such as cytokine release syndrome and hematologic toxicities. This study evaluates the prognostic significance of spleen size, measured via computed tomography (CT), in predicting clinical outcomes for RRMM patients undergoing CAR T-cell therapy. We retrospectively analyzed data from patients treated with Idecabtagene vicleucel or Ciltacabtagen autoleucel (N=73) and show that enlarged spleen size is associated with severe and prolonged thrombocytopenia, higher metabolic tumor volumes, and elevated soluble BCMA (sBCMA) levels. Our findings indicate that splenomegaly (>340 cm³) is an independent prognostic marker for both progression-free and overall survival, outperforming markers such as sBCMA levels, EASIX, and CAR- Hematotox scores. These results suggest that spleen size could enhance risk stratification in CAR T-cell therapy for RRMM patients, offering a readily accessible tool for guiding monitoring strategies and healthcare resource management.