Smoldering multiple myeloma risk factors for progression: a Danish population-based cohort study

Several risk scores for disease progression in Smoldering Multiple Myeloma (SMM) patients have been proposed, however, all have been developed using single center registries. To examine risk factors for time to progression (TTP) to Multiple Myeloma (MM) for SMM we analyzed a nationwide population-based cohort of 321 newly diagnosed SMM patients registered within the Danish Multiple Myeloma Registry between 2005 and 2014. Significant univariable risk factors for TTP were selected for multivariable Cox regression analyses. We found that both an M-protein ≥ 30g/l and immunoparesis significantly influenced TTP (HR 2.7, 95%CI(1.5;4.7), p=0.001, and HR 3.3, 95%CI(1.4;7.8), p=0.002 respectively). High free light chain (FLC) ratio did not significantly influence TTP in our cohort. Therefore, our data do not support the recent IMWG proposal of identifying patients with FLC ratio above 100 as having ultra-high risk of transformation to MM. Using only immunoparesis and M-protein ≥ 30g/l, we created a scoring system to identify low, intermediate and high risk SMM. This first population-based study of SMM patients confirms that an M-protein ≥ 30g/l and immunoparesis remain important risk factors for progression to MM. This article is protected by copyright. All rights reserved.