Real-world assessment of treatment patterns and outcomes in patients with relapsed-refractory multiple myeloma in an Italian haematological tertiary care centre.

Despite significant improvements in therapeutic options, multiple myeloma (MM) patients experience a series of remissions and relapses requiring further lines of therapy (LOTs). We analysed treatment pathways, attrition rates (ARs) and refractoriness patterns across LOTs in 413 MM patients treated from 2011 and 2021. Across LOT-2 to LOT-5 ARs were 26%, 27%, 34% and 37.5%, being 50% for subsequent LOTs. In univariate analysis age over 65 years, international staging system (ISS) II/III, more than two comorbidities, no transplant and no maintenance therapy were significantly associated with AR but regression analysis selected only age over 65 years and more than 2 comorbidities. Median progression-free survival (PFS) was 40.5, 19.5, 10.3, 6 and 4.7 months from LOT-1 to LOT-5. Lenalidomide-refractory patients, among those relapsed after LOT-1, were 26% and 64.5% respectively, in patients starting therapy before 2019 versus in or after 2021. In the two cohorts, 57.5% and 85.5% of patients relapsed after LOT-2 were lenalidomide-refractory. Among patients not relapsed from LOT-1, 80% are receiving continuous lenalidomide and could become lenalidomide-refractory, whereas 91% and 51.5% of patients in LOT-2 could become potential lenalidomide- and daratumumab-refractory respectively. In our analysis the rate of patients reaching subsequent LOTs was higher than previously reported and the increase in early refractoriness would require faster and more efficient treatment licensing processes.