Immunoglobulin M Monoclonal Gammopathies of Undetermined Significance and Indolent Waldenström's Macroglobulinemia Recognize the Same Determinants of Evolution Into Symptomatic Lymphoid Disorders: Proposal for a Common Prognostic Scoring System

Abstract

Purpose To evaluate the clinicohematologic variables at diagnosis that are prognostically related to neoplastic progression in patients with immunoglobulin M (IgM) monoclonal gammopathies of undetermined significance (MGUS), and indolent Waldenström's macroglobulinemia (IWM), and propose a scoring system to identify subsets of patients at different risk. Patients and Methods We evaluated 217 patients with IgM MGUS and 201 with IWM (male-female ratio, 131:86 and 117:84; mean age, 63.7 and 63.6 years, respectively) diagnosed on the basis of serum monoclonal component (MC) levels and bone marrow lymphoplasmacytic infiltration degree. The variables selected by univariate analyses were multivariately investigated; on the basis of their individual relative hazards, a scoring system was devised to identify subsets of patients at different risk of evolution. Results After a median follow-up of 56.1 and 60.2 months, 15 of 217 MGUS and 45 of 201 IWM patients, respectively, required chemotherapy for symptomatic WM (13 and 36), non-Hodgkin's lymphoma (2 and 6) and amyloidosis (0 and 3). The median time to evolution (TTE) was not reached for MGUS and was 141.5 months for IWM. The variables adversely related to evolution were qualitatively the same in both groups: MC levels, Hb concentrations and sex. A scoring system based on these parameters identified three risk groups with highly significant differences in TTE in both groups (P < .0001). Conclusion MGUS and IWM identify disease entities with different propensities for symptomatic neoplastic evolution. As both have the same prognostic determinants of progression, we propose a practical scoring system that, identifying different risks of malignant evolution, may allow an individualized clinical approach.