Evolving M-protein pattern in patients with smoldering multiple myeloma: impact on early progression

Smoldering multiple myeloma (SMM) is a biologically heterogeneous, clinically defined entity with a variable rate of progression to symptomatic multiple myeloma (MM). Reliable markers for progression are critical for the development of potential therapeutic interventions. We retrospectively evaluated the predictive value of the evolving pattern of serum M-protein among other progression risk factors in 206 patients with SMM diagnosed between 1973 and 2012. Median time from recognition of evolving type to progression into symptomatic MM was 1.1 years (95% CI 0.5-2.0) and progression rate at 3 years was 71%. Development of the evolving type drastically worsened the prognostic estimation made at diagnosis for every covariate predictive of progression (serum M-protein size, bone marrow plasma cell infiltration, immunoparesis and Mayo Clinic risk). On average, the hazard ratio for progression to symptomatic MM increased to 5.1 (95% CI 3.4-7.6) after recognition of the evolving type. In conclusion, in patients with SMM the evolving pattern accurately predicts the risk of early progression to symptomatic disease, thereby allowing the identification of ultra-high risk patients who would be candidates for immediate therapy.