Delayed kidney response in AL amyloidosis: prevalence and clinical significance

Kidney involvement is frequent in AL amyloidosis and significantly impacts prognosis. Although hematologic response is the recommended marker for monitoring treatment efficacy, organ-specific responses are frequently evaluated in clinical practice. In this context, the significance and optimal timing of kidney-specific response remain poorly defined in the literature.

We conducted a retrospective study of patients with renal AL amyloidosis treated with or without anti-clonal therapy (ACT). Kidney response rates and their timing were analyzed. Patients were stratified by time to kidney response: very early (0-6 months), early (6-12 months), and late (>12 months). Baseline characteristics, treatments, and outcomes were compared across groups.

Seventy-six patients were included; 58 received ACT. Among them, 59% achieved hematologic response and 52% achieved kidney response. Kidney response was associated with improved kidney survival. Median time to hematologic response was 4.58 (1-9.38) months, whereas median time to partial and complete kidney response were 9 (6-18) and 16.5 (9-25) months (P = .03). Kidney outcomes were similar regardless of response timing. Patients with late kidney response had longer time to hematologic response (9.75 vs. 3 months, P = .02), longer treatment duration (24.5 vs. 9 months, P = .02), and received more ACT lines, particularly among those with very early hematologic response.

Kidney response in AL amyloidosis occurs later than hematologic response but is associated with favorable kidney outcomes. In our study, delayed kidney response was associated with longer treatment duration despite hematologic response. Prospective studies are needed to determine whether treatment decisions based on kidney response alone improve or worsen patient outcomes.