Outcomes of patients with AL amyloidosis and low serum free light chain levels at diagnosis

Abstract

Serum free light chains (sFLC) are independent prognostic markers of disease in light chain (AL) amyloidosis, and are used in the haematologic response criteria for treatment. However, up to 20% of patients have low sFLCs at diagnosis, with a difference between involved and uninvolved free light chains (dFLC) of less than 50 mg/L, making responses to treatment difficult to evaluate. In order to characterize this distinct subgroup of patients, we retrospectively analyzed 123 AL amyloidosis patients with dFLC <50 mg/L who were diagnosed between 2002 and 2013. The majority (n = 117) were treated for their AL amyloidosis, with over half (n = 68) receiving high-dose melphalan and autologous stem cell transplantation as first-line therapy. Overall they had a prolonged median survival of 9.2 years with less cardiac involvement (30%) and more renal involvement (76%). We also evaluated the newly proposed low dFLC partial response (PR) criteria, defined as a dFLC <10 mg/L if the initial dFLC 20–50 mg/L. The 14 patients with low dFLC PR had improved survival and organ responses compared with patients with no haematologic response. However, one-third of patients (n = 41) had an initial dFLC <20 mg/L so could not be evaluated. More sensitive methods of monitoring response to treatment for this subgroup population are still needed.

Keywords:

• AL amyloidosis
• stem cell transplantation
• survival
• immunoglobulin light chain
• haematologic response

Acknowledgements

A summary of the results of this study was presented at the XVth International Symposium on Amyloidosis in July 2016. The authors gratefully acknowledge the numerous colleagues in the Amyloidosis Center, Cancer Clinical Trials Office, and Center for Cancer and Blood Disorders at Boston Medical Center who assisted with the multidisciplinary evaluation and treatment of the patients with AL amyloidosis.

Disclosure statement

Authors declare no competing financial conflict.