The Importance of Kidney Response over Hematologic Response in Predicting Kidney Outcomes in AL Amyloidosis

Background: Light chain amyloidosis is a clonal plasma cell disorder characterized by amyloid fibril deposition in multiple organs. Kidney involvement of amyloidosis often leads to progression to end-stage kidney disease. This study aimed to identify predictors of kidney survival in patients with kidney amyloidosis, focusing on hematologic and kidney response. Methods: This retrospective study included 138 patients diagnosed with kidney amyloidosis between 2011 and 2019. Palladini et al.'s criteria were applied for kidney stage and response, and the 2012 International Society of Amyloidosis criteria for hematologic response. Kidney and hematologic response were assessed at 6 months after treatment initiation. Deep hematologic response was defined as the achievement of at least very good partial response. Results: Overall, 17 (12.3%) progressed to end-stage kidney disease. In multivariable analysis, kidney stage 2 was independently associated with an increased risk of end-stage kidney disease compared to stage 1 (hazard ratio [HR] 3.75; 95% confidence interval [CI] 1.38–10.15; P = 0.01). Compared to kidney response, the risk of end-stage kidney disease increased by 8.42 times (95% CI 1.71–41.35; P = 0.01) in stable disease and 7.36 times (95% CI 1.25–43.33; P = 0.03) in kidney progression. However, neither deep hematologic response nor the difference between involved and uninvolved free light chain, one component of hematologic response, showed an association with kidney outcome. Kidney survival was longer in patients with both deep hematologic response and kidney response than in those with only hematologic response (P = 0.004). Conclusion: The study underscores the importance of kidney response over hematologic response in predicting end-stage kidney disease and emphasizes the need to establish treatment endpoints, considering organ response alongside hematologic response.