Venous thromboembolism and risk of cancer in patients with rheumatoid arthritis

Abstract

Background It is unknown whether venous thromboembolism (VTE) in rheumatoid arthritis (RA) patients can be a marker of occult cancer. Objectives To examine risk of cancer subsequent to VTE among RA patients compared with risk of cancer in an RA cohort without VTE and in a general population without RA and without VTE. Patients/Methods All RA patients with a first-time diagnosis of VTE (index date) during 1978-2013 and comparison cohorts were identified from population-based registries in Denmark. Results We identified three cohorts: 2497 RA patients with VTE, 11672 RA patients without VTE and 12730 persons from the general population. The cumulative incidence of cancer within the first year of the index date was 3.2% among RA with VTE, 2.2% among RA without VTE, and 2.0% in the general population cohort. Incidence rate ratios (IRRs) were 1.79 (95% confidence interval [CI], 1.37-2.33) for RA patients with VTE vs. RA patients without VTE and 2.12 (95% CI, 1.63-2.76) for RA patients with VTE vs. the general population. The IRR of cancer at >1 to 36years from the index date among RA patients with VTE was 1.16 (95% CI, 1.00-1.34) compared with the RA patients without VTE and 1.33 (95% CI, 1.15-1.53) compared with the general population. Conclusions We found an increased risk of cancer in RA patients with VTE during the first year following VTE and also during the longer follow-up period. Thus, VTE may not only be a result of inflammation and immunological dysfunctions associated with RA, but may also be a marker for occult cancer.