Malignant plasma cells
A long-term study showed that patients with monoclonal gammopathy of undetermined significance (MGUS) were still at risk of progressing to other plasma-cell or lymphoid disorders after more than 30 years of follow-up.
The risk of developing such disorders was nearly 7 times higher in MGUS patients than in matched control subjects.
Patients with MGUS also had a significantly shorter median survival than controls.
Researchers reported these findings in NEJM.
“Monoclonal gammopathy of undetermined significance is present in more than 3% of the general population age 50 and older,” said study author S. Vincent Rajkumar, MD, of the Mayo Clinic in Rochester, Minnesota.
“In some cases, people with monoclonal gammopathy of undetermined significance go on to develop multiple myeloma.”
With this in mind, Dr Rajkumar and his colleagues studied 1384 patients—210 with IgM MGUS and 1129 with non-IgM MGUS. Patients were diagnosed with MGUS from 1960 through 1994, and their median age at diagnosis was 72.
The median follow-up was 34.1 years (range, 0.0 to 43.6), so there were 14,130 person-years of follow-up.
During that time, 147 patients progressed to another disorder, including:
- 97 to multiple myeloma
- 19 to non-Hodgkin lymphoma
- 14 to AL amyloidosis
- 13 to Waldenstrom’s macroglobulinemia
- 3 to chronic lymphocytic leukemia
- 1 to plasmacytoma.
The rate of progression in MGUS patients—11%—represented a risk of these disorders that was 6.5 times higher than the risk observed in an age- and sex-matched control population.
The risk of progression also increased over time for MGUS patients. Without accounting for death due to competing causes, the risk of progression was 10% at 10 years, 18% at 20 years, 28% at 30 years, and 36% at both 35 and 40 years.
“We also found that patients with monoclonal gammopathy of undetermined significance had shorter survival than comparable people without the condition, which raises the possibility there may be other disorders associated with monoclonal gammopathy of undetermined significance that still need further study,” Dr Rajkumar said.
The median survival was 8.1 years in MGUS patients and 12.4 years in controls (P<0.001).
Overall, 1300 MGUS patients (94%) had died at last follow-up. Of the 84 patients who were still alive, 5 had progressed.
