Background:: Venous thromboembolism (VTE) may be a harbinger of cancer. Inflammatory bowel disease (IBD) is known to increase the risk of VTE, but it is unclear whether VTE in IBD patients is also a marker for occult cancer. We assessed the risk of cancer after VTE in IBD patients.
Methods:: We conducted a population‐based cohort study by linking Danish medical registries during 1978–2008. We calculated standardized incidence ratios (SIRs) by comparing observed cancer incidence after VTE in IBD patients with that expected based on national cancer incidence in the Danish population.
Results:: A total of 895 IBD patients with VTE were followed for a total of 5290 person‐years. During the first year of follow‐up, 28 (3.1%) patients were diagnosed with cancer, corresponding to an SIR of 3.2 (95% confidence interval [CI]: 2.2, 4.7). Patients with ulcerative colitis or Crohn's disease had similar relative risks (SIR = 3.1 [95% CI: 1.9, 4.9] and SIR = 3.5 [95% CI: 1.7, 6.3], respectively). In IBD patients <55 years the SIR was 5.7 (95% CI: 2.3, 11.8) and in patients ≥55 years the SIR was 2.8 (95% CI: 1.8, 4.3). During the second and subsequent years of follow‐up 61 cancers were diagnosed (SIR = 1.2 [95% CI: 0.92, 1.6]).
Conclusions:: In patients with IBD a VTE event is not only a consequence of their disease, but might also be a marker of occult cancer. We suggest that IBD patients with VTE should follow the same diagnostic work‐up guidelines as non‐IBD VTE patients. (Inflamm Bowel Dis 2012)