No Risk of Arterial or Venous Thrombosis in Monoclonal Gammopathy of Undetermined Significance: Results from a Population-Based Study

Background

Monoclonal gammopathy of undetermined significance (MGUS) is a precursor condition to multiple myeloma (MM) and other lymphoproliferative disorders. Patients with MM have an increased risk of venous and arterial thrombosis. Results from previous studies have also shown an increased risk of thrombosis in MGUS. However, these studies have been performed on clinically established cohorts, and no previous study has examined the risk of thrombosis in light chain MGUS (LC-MGUS).

Methods

We performed a population-based study on the longitudinal cohort of the AGES-Reykjavik Study, consisting of 5,764 elderly Icelandic men and women. Through screening all participants with free light chain analysis and serum protein electrophoresis, MGUS and LC-MGUS were identified in 299 and 52 individuals, respectively. The outcome was first incidence/occurrence of venous or arterial thrombosis, as diagnosis or as cause of death. Information on outcomes was supplemented by health care records, available from nine years prior to study baseline and for a median follow-up time of 8.8 years. Through logistic regression, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate history of arterial and venous thrombosis, respectively, at study baseline. A Cox proportional hazards model was used to estimate hazard ratios (HRs) and 95% CIs for the risk of first incidence of thrombosis during follow-up.

Results

A history of any thrombosis during the nine years prior to diagnosis was present in 30 (10.0%) of individuals with MGUS, 13 (25.0%) of individuals with LC-MGUS, and 643 (12.0%) of individuals without MGUS. In a model adjusting for age, sex, smoking, serum cholesterol levels, diabetes, hypertension, and family history of thrombosis, the odds of having had a thrombosis was not significantly different for neither MGUS (OR = 0.75, 95% CI 0.50-1.12) nor LC-MGUS (OR = 1.81, 0.92-3.58), compared to those without MGUS.

During a median follow-up time of 8.8 years, 80 (26.8%) of individuals with MGUS, 14 (26.9%) of individuals with LC-MGUS, and 1,344 (25.0%) of individuals without MGUS were diagnosed with thrombosis. Individuals with MGUS and with LC-MGUS had no increased risk of arterial thrombosis, when adjusted for age, sex, cholesterol, diabetes, hypertension, smoking, and family history of thrombosis (HR 1.04, 0.82-1.32). Similarly, no increased risk was found in MGUS or LC-MGUS for venous thrombosis, in a model adjusted for age, sex, body mass index, and previous or current cancer (HR 0.89, 0.41-1.89). Excluding individuals with a diagnosis of thrombosis occurring before baseline, or adjusting for a personal history of thrombosis, did not affect the results.

Summary and conclusions

In this large, population-based, screening cohort study, we found no increased risk of arterial or venous thrombosis in MGUS. A history of thrombosis was more common in individuals with LC-MGUS, which might be an effect of higher age in LC-MGUS individuals. To our knowledge, this is the first study to investigate risk of thrombosis in LC-MGUS. The results from our screened study contradict previous findings from clinically established cohorts. Future work is needed to better understand observed differences between studies and across populations. For example, potential underlying factors may include aggregation of underlying comorbidities in clinically diagnosed MGUS patients, and biological variations (shared germline genetic susceptibility) by ethnic groups.