Treatment Patterns and Outcomes of Multiple Myeloma Patients Undergoing Second-Line Therapy: A Canadian Myeloma Research Group (CMRG) Analysis

INTRODUCTION: First-line treatment in Canadian transplant-eligible MM patients is CyBorD/RVD followed by ASCT and maintenance lenalidomide. In transplant ineligible patients, bortezomib- or lenalidomide-based treatment is used. Relapse options include salvage ASCT or diverse doublet/triplets. Limited data support any one approach. The aim of this study was to assess treatment patterns/outcomes of real-world patients at first relapse. METHODS: All patients initiating second-line therapy from January 1/10 to June 30/22 were included. We evaluated ORR, PFS and OS, calculated from the start of second-line. RESULTS: A total of 3569 patients were included, 1638 (45.9%) with prior ASCT and 1931 (54.1%) without. The most used regimens were Rd, DRd, CyBorD, ASCT, RVd and DVd. The highest ORRs were seen with DRd (90%), ASCT (89%), Kd/KCd (79%), RVd (78.1%) and KRd (74%). For drug regimens, median PFS (27.6 months) and OS (75.5 months) were longest for DRd. CONCLUSIONS: We evaluated impact of second-line treatment in MM patients. Triplets with an IMiD backbone and carfilzomib combinations had high ORR and durable PFS, with select patients undergoing second ASCT achieving durable responses. Given the expanding use of IMiD, PI and CD38 mAbs frontline, our results highlight the need for modern modalities at first relapse and provide a benchmark for implementation.