[Monoclonal gammopathies of undetermined significance and their progression over time. Retrospective study of 190 patients].

Introduction: Monoclonal gammopathies of undetermined significance (MGUS) occur in up to 1% of persons aged 50 years or older. The risk of its progression to multiple myeloma or related disorders is also approximately 1% per year.
Objectives: Our study had two aims: to describe the risk of malignant progression of patients examined in our center for MGUS, and to identify predictors of this malignant progression.
Methods: We retrospectively reviewed the medical records of patients with MGUS seen in our center from 1980 through 1995. Information about progression came either from the medical file or from responses to questionnaires sent to patients' general practitioners.
Results: The study included 190 patients. Median follow-up was 84 months (range: 12-240 months). MGUS remained stable for 128 patients (67.37%), whose median follow-up was 96 months. Malignant transformations occurred in 41 patients (21.58%). The median interval from diagnosis of MGUS to diagnosis of a lymphoplasma cell proliferative disorder was 49 months. The cumulative probability of progression was 13.05% at 5 years and 25.14% at 10 years. The initial concentration of serum monoclonal protein was a significant predictor of progression (threshold value: 15 g/L).
Discussion: The cumulative probability of progression in our study is higher than that observed elsewhere. Our results may well be biased by the short follow-up period and selective referrals.
Conclusion: The initial concentration of serum monoclonal protein is a significant predictor of malignant progression of MGUS.