Comparison of progression risk of monoclonal gammopathy of undetermined significance by method of detection.

Monoclonal gammopathy of undetermined significance (MGUS) is an asymptomatic pre-malignant disorder. The current standard of care is not to screen for MGUS, so it is often incidentally diagnosed in the clinic. It is unknown whether the outcomes of screened versus clinically detected MGUS differ. We compared the progression risk between screened versus clinical MGUS cohorts and assessed whether the MGUS detection method impacted risk prediction of established clinical factors (score). We included 379 screened MGUS from the Olmsted County population based study and 1384 MGUS patients diagnosed during routine clinical evaluation at Mayo Clinic. Median follow-up time for the screened versus clinical cohort was 26.6 and 40.1 years, respectively. Accounting for death as a competing risk, the cumulative incidence of progression at 25 years was similar in the screened (11.1% [95% CI 8.3-14.8]) versus clinical (10.1% [95% CI 8.6-11.8%]) MGUS cohorts, even when stratified by sex, age, or the baseline MGUS risk score. Overall, 0.9 (95% CI 0.6-1.2) screened versus 1.0 (95% CI 0.9-1.2) clinically detected MGUS patients experienced disease progression for every 100 person years of follow-up. MGUS detection method did not modify the association between MGUS risk score and progression risk (pinteraction=0.217) and did not add to known risk factors for progression (likelihood ratio test, p=0.839). Here we show that progression risk among patients with screened versus clinically detected heavy-chain MGUS was similar. Future studies are needed to assess if tailored follow-up of screened MGUS patients affects clinical outcomes.