A detailed evaluation of the current renal response criteria in AL amyloidosis: is it time for a revision?

Organ response correlates with overall survival in patients with immunoglobulin light chain amyloidosis and is the goal of treatment. This study evaluates the current renal response criteria and their ability to predict overall survival. Patients with immunoglobulin light chain amyloidosis who underwent autologous stem cell transplantation between 1995 and 2010 were recruited. Eligibility criteria included >1 g/dL of proteinuria, dialysis independence at baseline and within the first year of autologous stem cell transplantation, and a minimum follow-up of 1 year. Responses were assessed by the best values after autologous stem cell transplantation. The difference between involved and uninvolved serum free light chain levels was used to determine hematologic response. Increases in serum creatinine were calculated from the highest creatinine after autologous stem cell transplantation. Inclusion and exclusion criteria were met by 141 patients. These patients had a median follow-up of 52 months. Superior overall survival was observed in patients with a >75% reduction in proteinuria and those who had a >95% reduction had additional benefits. The overall survival of patients with >50% to ≤75% proteinuria was similar to that of patients with ≤50% reduction. A rise in serum creatinine >25% was not associated with a poorer outcome in patients with a >75% reduction in proteinuria. Deeper hematologic responses were associated with higher rates of proteinuria reduction. These results suggest that further evaluation of the current renal response criteria is needed. In particular, discrimination of the renal response into complete and partial categories and modification of the serum creatinine requirement seem justified.