Background-smoldering multiple myeloma (SMM) risk of progression to multiple myeloma (MM) is highly heterogeneous and several models have been suggested to predict this risk. Lakshman et al. recently proposed a model based on three biomarkers: bone marrow plasma cell (BMPC) percentage > 20%, free light chain ratio (FLCr) > 20 and serum M protein > 20 g/L. The goal of our study was to test this "20/20/20" model in our population and to determine if similar results could be obtained in another cohort of SMM patients. Method-we conducted a retrospective, single center study with 89 patients diagnosed with SMM between January 2008 and December 2019. Results-all three tested biomarkers were associated with an increased risk of progression: BMPC percentage ≥ 20% (hazard ratio [HR]: 4.28 [95%C.I., 1.90-9.61]; p < 0.001), serum M protein ≥ 20 g/L (HR: 4.20 [95%C.I., 1.90-15.53]; p = 0.032) and FLCr ≥ 20 (HR: 3.25 [95%C.I., 1.09-9.71]; p = 0.035). The estimated median time to progression (TTP) was not reached for the low and intermediate risk groups and was 29.1 months (95%C.I., 3.9-54.4) in the high-risk group (p = 0.006). Conclusions-the 20/20/20 risk stratification model adequately predicted progression in our population and is easy to use in various clinical settings.
Keywords: multiple myeloma; risk stratification model; smoldering multiple myeloma.