Cumulative probability of disease progression among patients with different risk scores according to the proportional hazards model and model performance in external validation cohorts. (A) The model was built using four variables: BM involvement, immunoglobulin M (IgM) levels, β2-microglobulin, and albumin. It divided the cohort into three risk groups, corresponding to low-, intermediate-, and high-risk AWM with a median time to progression (TTP) of 9.3, 4.8, and 1.8 years, respectively. Dashed and solid lines represent the results of training set and cross-validation, respectively. (B) Mayo Clinic, Rochester, MN, cohort: median TTP of 10.2, 5.7, and 2.4 years, for the low-, intermediate-, and high-risk groups, respectively. (C) National and Kapodistrian University, Athens, Greece, cohort: median TTP of not reached, 7.3, and 2.9 years, for the low-, intermediate-, and high-risk groups, respectively. BM, bone marrow; AWM, Asymptomatic Waldenström macroglobulinemia.