Impact of extramedullary multiple myeloma on outcomes with idecabtagene vicleucel.

Idecabtagene vicleucel (Ide-cel) has demonstrated excellent efficacy and durable responses in patients with relapsed/refractory multiple myeloma (RRMM). However, the outcomes with ide-cel in patients with extramedullary disease (EMD) remain incompletely characterized. We included patients with RRMM treated with ide-cel between May 2021 and April 2023 across 11 US academic institutions. Visceral or soft tissue lesions non-contiguous from bone was classified as EMD. Time-to-event analyses were performed from date of ide-cel infusion. Among 351 patients, 84 (24%) had EMD prior to infusion. The median follow-up from ide-cel infusion was 18.2 months (95% CI: 17-19.3). The day 90 overall response rates (ORR) were 52% vs. 82% for the EMD and non-EMD cohorts, respectively (p < 0.001). The median progression-free survival (PFS) was 5.3 months (95% CI: 4.1-6.9) for the EMD cohort vs. 11.1 months (95% CI: 9.2-12.6; p < 0.0001) for the non-EMD cohort. In a multivariable analysis, EMD was an independent predictor of inferior PFS [hazard ratio 1.5 (1.1-2.2), p = 0.02]. The median overall survival was 14.8 months [95% CI: 9-Not reached (NR)] vs. 26.9 months (26.3 vs. NR, p = 0.006) for the EMD and non-EMD cohorts, respectively. Extramedullary disease represents an independent predictor of inferior day 90 ORR and PFS among patients treated with ide-cel.