Prognostic risk and survival of asymptomatic IgM monoclonal gammopathy: Results from a Spanish Multicenter Registry.

Asymptomatic IgM gammopathy encompasses IgM monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic Waldenström macroglobulinemia (AWM), both having a risk of progression to symptomatic disease. Here, we assessed the risk of progression and the mortality of 956 patients with asymptomatic IgM gammopathy across 25 Spanish centers. After a median follow-up of 5.7 years, 156 patients progressed, most of them to symptomatic WM (SWM). The cumulative incidence of progression was 13% and 20% at 5 and 10 years, respectively. The serum IgM ≥10 g/L, bone marrow (BM) infiltration ≥20%, β2-microglobulin ≥3 mg/L, and albumin <4 g/dL were the most potent predictors of disease progression in a multivariate Cox regression model, allowing the identification of three risk categories. The probability of progression to symptomatic disease at 5 years was 4.5%, 15.7%, and 42.8% for low-, intermediate-, and high-risk groups, respectively. In patients without a BM evaluation, the presence of none or 1 risk factor and 2 or 3 risk factors conferred a progression risk of 6% and 27% at 5 years, respectively. The model was independent of the presence of