Clinical question: What is the expected clinical progression of patients with monoclonal gammopathy of undetermined significance (MGUS)?
Study design: Prospective, observational cohort study.
Setting: Single institution in Minnesota.
Synopsis: Investigators identified 1,395 patients with MGUS during 1960-1994, with a median follow-up of 34 years. Progression to multiple myeloma, plasma cell disorders, or lymphoid disorders was noted in 147 patients (11%), which represents a 6.5-times higher risk for these disorders, compared with the age/sex–adjusted control population.
Two risk factors were associated with progression of disease: elevated serum M protein (greater than 1.5 g/dL) and an abnormal serum free light chain ratio. Risk of progression at 20 years in patients with both of these risk factors was 55% in patients with IgM subtypes and 30% in patients with non-IgM subtypes. With a single risk factor, risk of progression at 20 years was 41% and 20%, respectively. With no risk factors the risk of progression at 20 years was 19% and 7%. Overall expected survival was shorter in patients with MGUS versus that in the age/sex–matched control population.
Bottom line: Patients with MGUS have a shorter life expectancy than the general population, and the IgM subtype is associated with a greater risk of progression at 20 years, compared with the non-IgM subtype.
Citation: Kyle RA et al. Long-term follow-up of monoclonal gammopathy of undetermined significance..
Dr. Thota is a hospitalist at UC San Diego Health and an assistant clinical professor at the University of California, San Diego.