Abstract
Background: Daratumumab (DARA), lenalidomide (LEN), and dexamethasone (DEX, DRd) are one of standards of care for patients with multiple myeloma (MM); however, the clinical impact of relative dose intensity (RDI) remains unclear. In this retrospective study, the aim was to analyze the relationship between the RDI and clinical outcomes in patients with myeloma treated with DRd. Methods: The numbers of patients with newly diagnosed, relapsed, and/or refractory MM were 40 and 71, respectively. Results: The median patient age was 74 years, and the median RDIs for DARA, LEN, and DEX were 84.0%, 39.4%, and 14.6%, respectively. At a median 26.8 months follow-up interval, the 2-year time to the next treatment (TTNT) of the high RDI of DARA (cutoff, 90%) was greater than that of the low RDI of DARA (77.3% vs. 51.6%, p < 0.001), and the 2-year overall survival (OS) of the low RDI of DEX (cutoff, 15%) was longer than that of the high RDI of DEX (87.7% vs. 61.0%, p = 0.027). Multivariate analysis showed that a high RDI for DARA and low RDI for DEX were associated with longer TTNT and OS (hazard ratio, 0.503, p = 0.044; hazard ratio 0.426, p = 0.022, respectively). The high RDI of DARA and low RDI of DEX reduced the incidence of severe infections (p = 0.040 and 0.049). Conclusion: The high RDI of DARA and low RDI of DEX predicted good clinical outcomes in this study's cohort.