Extended Use of Serum Free Light Chain as a Biomarker in Lymphoproliferative Disorders A Comprehensive Review

Serum free light chain (sFLC) assays were shown to improve detection, management, and prognostication in plasma cell disorders. Recently, sFLC assays improved detection of AI proteins when combined with standard methods of protein electrophoresis/immunofixation in patients with non-Hodgkin lymphoma/chronic lymphocytic leukemia (NHL/CLL). Incidence of abnormal sFLC ratio (sFLCr) varied from 0% to 36% and 29.7% to 59% in NHL and CLL, respectively. Increased sFLC levels or abnormal sFLCr predict shorter overall survival in early-stage CLL. Furthermore, abnormal sFLCr correlated with advanced disease stage and poorer outcome. In diffuse large B-cell lymphomas, increased sFLC was demonstrated as an independent, adverse prognostic factor for overall/event-free survival. Moreover, abnormal sFLCr can be a diagnostic tool in central nervous system lymphomas. Finally, the quantitative FLC assay has the potential to become a new, easily measured biomarker for predicting prognosis and enhanced detection in NHL/CLL. It may be used serially at follow-up evaluations to provide clues to relapse.