Late phase transfusion after CAR T therapy is associated with persistent hematotoxicity and non-relapse mortality in multiple myeloma: a post hoc analysis

BACKGROUND: Chimeric antigen receptor T-cell (CAR-T cell) therapy is highly effective for relapsed/refractory multiple myeloma (R/R MM), but hematologic toxicity and the need for blood transfusions remain common. This study examined the patterns of transfusion needs in patients receiving CAR-T cell therapy, analyzed risk factors, and assessed the effects of transfusions on clinical outcomes. METHODS: This retrospective study included 155 R/R MM patients treated with CAR-T cells targeting different antigens. We used multivariate regression and survival analysis to identify risk factors for early (≤ 30 days) and late (> 30 days) transfusion requirements and analyzed their prognostic impact. RESULTS: Of the 155 patients, 38.7% required transfusion in the early phase (≤ 30 days) and 35.5% in the late phase (> 30 days). Early transfusion was associated with acute inflammation and baseline bone marrow reserve but had limited impact on survival. In contrast, late transfusion, particularly red blood cell (RBC) transfusion, was associated with poor outcomes, including significantly reduced overall survival (median OS: 10.87 vs. 37.87 months; P < 0.0001) and progression-free survival (median PFS: 4.93 vs. 17.17 months; P < 0.0001). Late transfusion also correlated with a shallower depth of response (P < 0.001) and higher non-relapse mortality (P = 0.026). CONCLUSIONS: Transfusion requirement after CAR-T cell therapy is a key prognostic factor in MM. The need for early transfusion indicates high inflammation and severe acute toxicity, whereas the need for late transfusion is associated with poor remission, higher non-relapse mortality, and shorter survival. Reducing the need for transfusions could be important for lowering patient burden and improving outcomes.