Abstract
Hematologic complete response (hemCR) in AL amyloidosis requires absence of monoclonal protein by immunofixation electrophoreses (IFE) and normal serum free light chain ratio (FLCR). Recent literature suggests that an involved free light chain (iFLC) <20 mg/L or difference in free light chains (dFLC) <10 mg/L may more accurately predict outcomes after treatment. We evaluated overall survival in 340 patients treated with high-dose melphalan and stem cell transplantation (SCT). Of 305 patients evaluable 6 months after SCT, 90 (30%) achieved hemCR, 132 (43%) dFLC <10 mg/L, 118 (39%) iFLC <20 mg/L, and 176 (58%) normal FLCR. Of 215 patients without hemCR, 65 (30%) had dFLC <10 mg/L and 86 (40%) had normal FLCR. Overall survival (OS) in those achieving dFLC <10 mg/L or normal FLCR without hemCR was inferior to those achieving hemCR (p = 0.013 and p = 0.001). OS was not significantly different in patients achieving iFLC <20 mg/L without hemCR compared with hemCR (p = 0.243). Of those with hemCR, OS was not significantly improved if dFLC <10 mg/L was also achieved (p = 0.852), but OS was improved for those with hemCR who also attained iFLC <20 mg/L (p = 0.009). Multivariate analysis demonstrated absence of monoclonal protein in IFE and iFLC <20 mg/L as independent predictors of survival. Attainment of hemCR remains a treatment goal, although achieving iFLC <20 mg/L may also predict improved OS.
Highlights
Immunoglobulin light chain (AL) amyloidosis is a life threatening hematologic disorder characterized by deposition of amyloid fibrils formed from misfolded and aggregated clonal light chains
During the specified 16 years, a total of 340 patients with AL amyloidosis were treated with HDM/stem cell transplantation (SCT)
Our model demonstrates a trend toward improved Overall survival (OS) in patients with normal free light chain ratio (FLCR) (HR, 0.590; 95% confidence intervals (CI) 0.345–1.007; p = 0.053) (Table 2)
Summary
Immunoglobulin light chain (AL) amyloidosis is a life threatening hematologic disorder characterized by deposition of amyloid fibrils formed from misfolded and aggregated clonal light chains. Accumulation of amyloid fibrils leads to renal or cardiac dysfunction in the vast majority of patients. Treatment of AL amyloidosis is directed at the underlying clonal plasma or lymphoplasmacytic cells in the bone marrow that are the source of the amyloidogenic light chains. The current criteria used to evaluate hematologic response after treatment were developed in 2012 and validated in patients undergoing high-dose melphalan and stem cell transplantation. Transplantation Program in the Section of Hematology and Medical Oncology, Boston Medical Center, Boston, MA, USA Very good partial response (VGPR) is defined as a difference in involved and uninvolved serum free light chains (dFLC) < 40 mg/L and partial response (PR) as a decrease in the dFLC by >50% compared to baseline
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