Clinical Characteristics, Treatment Responses and Outcomes of Light Chain Multiple Myeloma

Light chain multiple myeloma (LCMM) is a subtype of multiple myeloma (MM) characterized by the exclusive production of immunoglobulin light chains and accounts for 15%-20% of newly diagnosed MM. A comprehensive comparison of LCMM with MM producing intact immunoglobulin (non-LCMM) remains limited. In this retrospective study, we described distinct clinical and cytogenetic features and assessed long-term outcomes in 852 LCMM patients diagnosed between 01/01/2004 and 12/31/2022, compared with non-LCMM controls matched for age, sex, and year of diagnosis. On univariable analysis, LCMM patients were more likely to present with elevated creatinine (> 2 mg/dL), beta-2-microglobulin ≥ 5.5 mg/L, elevated LDH, hypercalcemia, t(11;14), del(13q), and t(6;14). Conversely, IMS-IMWG high-risk disease, hyperdiploidy, t(4;14), and serum albumin < 3.5 g/dL were less common. On multivariable analysis, elevated creatinine (OR: 5.1, 95% CI: 1.2-27, p = 0.04), t(11;14) (OR: 2.6, 95% CI: 1.3-5.2, p = 0.006), and del(13q) (OR: 4.1, 95% CI: 2.1-8.2, p < 0.001) were independently associated with LCMM, while IMS-IMWG high-risk disease (OR: 0.3, 95% CI: 0.1-0.8, p = 0.02) and hyperdiploidy (OR: 0.3, 95% CI: 0.1-0.7, p = 0.002) were less frequent. Despite these differences, progression-free survival with frontline treatment (HR: 0.97, 95% CI: 0.84-1.11, p = 0.63) and overall survival (HR: 0.99, 95% CI: 0.87-1.13, p = 0.94) were similar between LCMM and non-LCMM patients. This study highlights the distinct clinical and cytogenetic features of LCMM, marked by higher rates of renal failure, t(11;14), and del(13q), lower prevalence of IMS-IMWG high-risk disease, and comparable survival outcomes.