Plasma Exchange in Myeloma‐Associated Acute Kidney Injury: A Multicenter Propensity‐Matched Cohort Study

ABSTRACT

Acute kidney failure from light chain cast nephropathy is a serious complication of multiple myeloma. Plasma exchange (PLEX) has been used to remove circulating free light chains (FLCs), but its benefit in the modern treatment era remains uncertain. We performed a retrospective multicenter cohort study using the TriNetX Research Network to identify newly diagnosed multiple myeloma cases presenting between 2014 and 2024 with acute kidney failure and FLC levels > 1500 mg/L. Patients were classified by receipt of PLEX within 7 days. Propensity score matching incorporated demographics, comorbidities, laboratory values, and initial myeloma‐directed therapies. The primary outcome was dialysis dependence at 90 days. Secondary outcomes included dialysis dependence at 180 days, mortality, renal recovery (creatinine < 2.0 mg/dL), ICU admission within 7 days, and dialysis‐free survival. Among 5454 eligible patients, 251 (4.6%) received PLEX. After matching, 248 patients were included in each group. PLEX was not associated with reduced dialysis dependence at 90 (16.1% vs. 18.1%; OR 0.87, 95% CI 0.54–1.39) or 180 days (18.5% vs. 20.2%; OR 0.90, 95% CI 0.58–1.41). Mortality, ICU admission, and dialysis‐free survival were also similar. PLEX was not associated with improved dialysis independence or survival, supporting rapid initiation of effective anti‐myeloma therapy.