Outcomes of Patients With Extramedullary Disease in Triple-Class Exposed Relapsed/Refractory Multiple Myeloma From the Pooled LocoMMotion and MoMMent Studies

Background: Patients with relapsed/refractory multiple myeloma (RRMM) who develop extramedullary disease (EMD) generally have a poor prognosis, highlighting the urgent need for new therapies. We report effectiveness outcomes and safety in patients with and without EMD from the pooled analysis of LocoMMotion and MoMMent. Methods: LocoMMotion and MoMMent-1 are prospective, noninterventional, consecutive studies assessing the evolving standard of care from 20192022 in patients with triple-class exposed RRMM. Results: Of 302 patients, 29 had EMD per investigator discretion and only 15 patients were assessed as having true extramedullary plasmacytoma (EMP; defined as patients with ≥1 EMP lesion) by the response review committee. The 29 EMD patients received 21 unique regimens (most commonly chemotherapy-based regimens). Of the 29 patients with EMD, overall response rate (ORR) was 24.1%, median progression-free survival (PFS) was 2.66 months, median overall survival (OS) was 7.16 months, and median time to next treatment (TTNT) was 3.09 months. All responses were lower (ORR) and shorter (median PFS, OS, and TTNT) in patients with EMD vs patients without EMD. Nineteen (65.5%) patients with EMD received ≥1 subsequent lines of therapy. Of those, two (10.5%) patients received bispecific antibodies and achieved a partial response or better; three (15.8%) patients received antibody-drug conjugates (responses were unknown or not determined at data cut-off), and no patients received chimeric antigen receptorT cell therapy. Conclusions: These results demonstrate the urgent need for more effective novel therapies for patients with EMD and highlight the need to use clear definitions of EMD and EMD response criteria for clinical trials.