Light chain monoclonal gammopathy of undetermined significance is characterized by a high disappearance rate and low risk of progression on longitudinal analysis.

We determined the 10-year progression rate of light chain monoclonal gammopathy of undetermined significance (LCMGUS) and investigated potential associations with cancer utilizing the German population-based Heinz Nixdorf Recall Study. The Heinz Nixdorf Recall Study comprises 4814 men and women aged 45-75 years. Serum samples from baseline (2000-2003) and five-year (2006-2008) and 10-year (2011-2015) follow-up examinations were screened for monoclonal free light chains (FLC). LCMGUS was defined as abnormal FLC ratio, increase of involved FLC with complete loss of immunoglobulin heavy chain, and absence of a history of lymphoproliferative disease (LPD). Seventy-five individuals with LCMGUS were identified across all three evaluation time points (median age 64 years; 43 (57%) male; FLCR > 1.65 65 (87%); FLCR ≤ 0.65 10 (13%)). After a median observation time of 11.5 years, none of the LCMGUS cases had progressed to overt LPD; in particular, we did not observe incident light chain multiple myeloma. On serial analysis 17/31 (55%), LCMGUS could not be confirmed and disappearance of the monoclonal protein was associated with low concentrations of the involved FLC. Individuals with LCMGUS had a 1.5-fold increased risk of cancer but did not show differences in overall survival or renal function as compared to individuals with normal FLC. In conclusion, LCMGUS represents a relatively benign condition with a high disappearance rate of the monoclonal protein on longitudinal analysis and normal overall survival at least in the population-based setting.