Venous Thromboembolism (VTE) in Patients (pts.) with Monoclonal Gammopathy of Undetermined Significance (MGUS)

Introduction: MGUS is considered to be a pre-malignant condition, and previous studies have reported VTE as a marker for a subsequent malignancy. We conducted a retrospective study to evaluate the incidence of VTE among MGUS patients (pts) and to correlate this incidence with different risk groups for developing malignancy in MGUS pts.

Methods: The complete medical records of all MGUS pts at Cleveland Clinic Cancer Center at Fairview hospital from Jun/2005–Jun/2008 were retrospectively reviewed. Of 237 pts diagnosed with MGUS, 112 pts (65 males, 47 females) were eligible for our study. These pts were divided into 2 risk groups: low risk (LR)/low-intermediate risk (LIR) group (78 pts.) and high intermediate risk (HIR)/high risk (HR) group (34 pts) based on the Risk Stratification Model using three adverse risk factors; serum M-protein level ≥ 3 gm/dL, non-IgG MGUS, and an abnormal kappa/lambda free light chain ratio. Only pts with ≥ 12 months follow up were included. Exclusion criteria included a personal history of inherited thrombophilia, previous episode of VTE or anticoagulant treatment, thrombocytosis, malignancy, and renal impairment. Risk factors (RF) for VTE were identified in each pt and categorized into four groups: no RF, 0; one RF, 1; two RF, 2; and > 2 RF, >2. RF included > 48 hours of immobilization, surgery in the past 3 months, current hospitalization at the time of VTE occurrence, oral contraceptive use, and congestive heart failure.

Objectives:

1. To compare the proportion of pts with MGUS who developed VTE to the proportion of pts in the general population who developed VTE.

2. To compare VTE incidence between the two risk groups.

Results: During the study period, 9 pts with MGUS experienced VTE. In the general population, the incidence of VTE is 117/100,000 persons/year (from literature). Therefore, the proportion of pts in the general population over 3 years was 117/100000 × 3 =0.0035. The proportion of VTE in MGUS pts, adjusted for 3 years, of 0.080 is significantly higher than that for the general population (p<0.001). Comparison of VTE incidence between the two risk groups, while adjusting for the number of risk factors, showed no difference (Cox Proportional Model, p=0.38). There is no significant difference in the risk of VTE among different levels of risk factors (p=0.96). The Kaplan-Meier estimates of the proportions of pts free of VTE at 24 months are 0.96 and 0.93 for the LR/LIR and HIR/HR groups, respectively.

Conclusions: MGUS is associated with a significantly higher rate of VTE compared to the general population. Despite many studies indicating VTE as a marker for subsequent malignancy, we did not find a difference in the incidence of VTE among the various risk factor groups. Any suggestive signs of VTE in pts with MGUS should be promptly evaluated and treatment initiated as soon as possible. Since the number of pts is small and the period of follow-up relatively short, a prospective cohort study is needed to verify our results.

Table?: Comparison of event rate: