Histological regression of amyloid in AL amyloidosis is exclusively seen after normalization of serum free light chain

Background Histological regression of amyloid has not been studied systematically but is assessed by clinical parameters. We analyzed the change of amyloid deposition in fat tissue in patients with AL amyloidosis following chemotherapy and studied the relation with type of hematologic response. Design and Methods Between January 1994 and July 2007 all consecutive patients with AL amyloidosis were evaluated in whom fat tissue aspirate was obtained before and following chemotherapy. Patients were divided into three groups depending on response of serum free light chain: complete, partial or non-responders. Fat tissue was assessed using a validated semi-quantitative test (grading 0-4). A change of 2 grades of amyloid deposition in fat tissue was considered significant and used as event to construct Kaplan-Meier curves of the patients who were able to reflect such a change. Results One hundred and twenty consecutive patients were studied. Fifty-one patients fulfilled inclusion criteria. Thirty patients had a complete response of the amyloidogenic free light chain a median 0.5 year (range 0.3-2.9 years) following chemotherapy. Reduction of 2 grades of amyloid deposition in fat tissue was seen in 50% of these patients after 2.4 years and in 80% after 3.2 years. In contrast to complete responders, none of the patients with partial (n=9) and non-response (n=12) showed reduction of 2 grades (p=0.02) with median follow-up of fat tissue analysis of 1.3 and 0.8 years, respectively. Conclusions This study in a selected group of patients with AL amyloidosis shows significant histological regression of amyloid deposition in fat tissue exclusively after normalization of serum free light chain.