Predictors of renal response in <scp>AL</scp> amyloidosis following anti‐plasma cell therapy: The impact of baseline serum free light chain levels and light chain isotype

Renal response (RenR) in light-chain (AL) amyloidosis is associated with a lower risk of end-stage kidney disease and improved survival. However, substantial variation exists in the time to and depth of RenR. We investigated variables associated with RenR in a retrospective study of newly diagnosed AL amyloidosis patients (n = 350) assessable for RenR between 2010 and 2022. RenRs were recorded at 6, 12 and 24 months and best response. Deep RenR was defined as a ≥renal very good partial response (RenVGPR, >60% reduction in 24-h proteinuria or ≤200 mg). Logistic regression and competing risk methods were used to examine variables associated with RenR. The median age was 64 years, and median follow-up was 5.5 years. On multivariable logistic regression, obtaining ≥HemVGPR within 6 months, kappa isotype, high baseline difference between involved and uninvolved free light chains (dFLC ≥40 mg/dL), renal stage and autologous haematopoietic stem cell transplant (AHSCT) were significantly associated with deep RenR. Cumulative incidence rates for deep RenR, treating death or renal progression as a competing event, demonstrated that early HemR, first-line AHSCT, lower renal stage and dFLC ≥40 mg/dL significantly increased the likelihood of deep RenR. Specific clonal plasma cell features, namely light-chain isotype and baseline dFLC levels, independently influence the timing and depth of RenRs in AL amyloidosis following treatment, in addition to renal stage and HemR.