Monoclonal Gammopathy of Undetermined Significance: Risk for Progression to Cancer, Other Disorders Examined

By Kelly Young

Edited by Susan Sadoughi, MD

Monoclonal gammopathy of undetermined significance (MGUS) is associated with an annual 1% risk for progression to multiple myeloma or plasma-cell or lymphoid disorder, and risk is higher for IgM MGUS, a long-term study in the New England Journal of Medicine finds.

Researchers studied nearly 1400 patients in Minnesota who were diagnosed with MGUS (median age at diagnosis, 72 years). During a median 34 years' follow-up, 11% developed multiple myeloma or plasma-cell or lymphoid disorder — a rate 6.5 times higher than that of the background population matched for age and sex.

Patients with IgM MGUS were at higher risk for progression than patients with non-IgM MGUS (relative risks, 11 vs. 6). In IgM MGUS, the presence of two risk factors (abnormal serum free light-chain ratio, high serum M protein levels) carried a 20-year risk for progression of 55%.

Overall, survival was shorter in patients with MGUS than in the general population (median, 8 vs. 12 years).