Prolonged Cytopenia After Idecabtagene Vicleucel for Multiple Myeloma is Associated with Poor Overall Survival

Background Cytopenias are well-recognized toxicities of idecabtagene vicleucel (ide-cel), a chimeric antigen receptor T cell (CAR-T) therapy approved for the treatment of relapsed, refractory multiple myeloma (RRMM). However, little is known of prognostic implications of cytopenias that persist 30 to 100 days after CAR-T infusion. Objective We report the duration, incidence, and impact on outcomes of post-CAR-T cytopenias at Day 30 and Day 100, defined as an absolute neutrophil count of < 500 cells/mm 3 and/or platelet count < 20 × 10 9 cells/L, per the recent definitions of immune effector cell–associated hematotoxicity for neutropenia (N-ICAHT) and thrombocytopenia (T-ICAHT). Study Design Using observational data from the Center for International Blood and Marrow Transplant Research, we identified 821 patients treated during 2021-2023. Results The cumulative incidence of cytopenias at Day 30 was 25% and at Day 100 was 2%. Patients with Day 30 cytopenias had inferior progression-free survival (PFS) (39% vs 45%, P = .01) and overall survival (OS) at 12 months (57% vs 76%, P < .01). While there was no significant difference in PFS in patients who had Day 100 cytopenias (42% vs 53%, P = .12), compared to those who did not, patients with Day 100 cytopenias had significantly inferior OS at 12 months (55% vs 82%, P < .01). High (≥ 2) CAR-HEMATOTOX score was associated with cytopenias at Day 30 (hazard ratio 5.26, P < .001). Conclusion Cytopenias at Day 30 after ide-cel were associated with inferior PFS and OS. In addition, cytopenias at Day 100 after ide-cel are rare and are associated with inferior OS.