Clinical question: What is the expected clinical progression of patients with monoclonal gammopathy of undetermined significance (MGUS)?
Background: There are few studies showing the risk of malignant transformation and survival in patients with MGUS. Additionally, there is limited data risk stratifying between the two subtypes of IgM and non-IgM 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.