Baseline Serum Albumin and Proteinuria Predict Renal Response after Autologous Stem Cell Transplantation in AL Amyloidosis.

Introduction: High dose melphalan followed by autologous stem cell transplantation (ASCT) is an effective treatment for patients with light chain associated (AL) amyloidosis. Longer patient survival and higher rates of organ response have now been documented by multiple studies. However, predictors of organ response remain unknown. Previously, we have reported the benefits of renal response after ASCT in this population. This study was conducted to investigate the characteristics that would predict renal response after ASCT.

Methods: The study was performed retrospectively on consecutive patients that underwent ASCT at our institution from March of 1996 to December of 2004. Exclusion criteria include baseline proteinuria < 1 g/d, dialysis prior to ASCT and lack of laboratory data at follow up to determine renal response. Renal response was defined by > 50% reduction in baseline proteinuria with < 25% decline in renal function as measured by serum creatinine. Treatment related mortality and dialysis dependence prior to meeting criteria of response were viewed as treatment failures. Hematologic response was determined by 50% reduction of monoclonal protein (free light chain) or complete eradication if the monoclonal protein was too small to be quantified.

Results: A total of 135 patients met criteria for study. Median age was 56.2 years at the time of transplant, 53.7% were male. Median baseline proteinuria and GFR were 6.4 g/d and 70 ml/min/1.73m2 respectively. Renal response was achieved in 35.6% of the patients while hematologic response was 71.1% in the 128 patients evaluated. Patient’s age, sex, albumin, GFR, proteinuria, conditioning regimen, and hematologic response were evaluated and the following were found to be associated with renal response: albumin (p = 0.001), proteinuria (p = 0.008), and hematologic response (p = 0.0002). The cutoff for albumin was found to be 1.6 mg/dl and proteinuria was 3.5 g/d. Multivariate analysis using a logistic regression model showed hematologic response and proteinuria to be independent predictors of renal response. The impact of proteinuria and hypoalbuminemia was then investigated together (Table 1). When combined, they were a better predictor then either one alone (Hazard ratio = 6.34 for combined, 3.43 for proteinuria, 3.32 for hypoalbuminemia). The combination was also a better independent predictor of renal response in the multivariate analysis. In this group of patients, renal response was associated with longer survival but hematologic response was not (p = 0.02).

Discussion: Our study showed that besides hematologic response, baseline serum albumin and proteinuria are independent predictors of renal response in AL patients after ASCT. Hypoalbuminemia and nephrotic range proteinuria, both markers of the severity of renal disease, have strong negative impact on response. This implies that there may be a limit to the reversibility of organ damage even when hematologic response is achieved. This study also points out the importance of organ (renal) response in this disease as hematologic response alone did not predict long term outcome. Our results suggest ASCT should be done early for AL to insure optimal organ response and patient outcome.