Smoldering Multiple Myeloma Prognosis

Smoldering or asymptomatic multiple myeloma (SMM) is a plasma cell dyscrasia characterized by a serum monoclonal protein level of 30 g/L or more or a proportion of plasma cells in the bone marrow of 10% or more but no evidence of end-organ damage. Individuals with SMM have a high-risk of progression to future symptomatic multiple myeloma or amyloidosis. A study from the Mayo Clinic followed 276 patients with SMM over a 26-year study period to establish prognostic factors for progression. The risk of progression was not constant over time. The overall risk of progression was 10% per year for the first 5 years, approximately 3 % per year for the next 5 years, and 1% per year for the last 10 years; the cumulative probability of progression was 73% at 15 years. The proportion of plasma cells in the bone marrow and the serum monoclonal protein concentration were combined to create a risk-stratification model with three distinct prognostic groups.