Superficial and deep venous thrombosis, pulmonary embolism and subsequent risk of cancer

BACKGROUND: In contrast to deep venous thrombosis and pulmonary embolism, superficial venous thrombosis has not been considered to be a marker of occult cancer. However, actual data regarding the association are very limited. METHODS: We identified all patients in Denmark from 1994 to 2009 with a diagnosis of superficial venous thrombosis, deep venous thrombosis in the legs or pulmonary embolism using population-based health registries. The occurrence of cancer in the three venous thromboembolism cohorts was compared with the expected numbers of cases estimated using national incidence rates to compute standardised incidence ratios (SIRs). FINDINGS: We identified a total of 7663 patients with superficial venous thrombosis, 45,252 with deep venous thrombosis and 24,332 with pulmonary embolism. In the first year of follow-up, very similar proportions of patients in the three cohorts were diagnosed with cancer. The SIR was 2.46 (95% CI, 2.10-2.86) for superficial venous thrombosis, 2.75 (95% CI, 2.60-2.90) for deep venous thrombosis, and 3.27 (95% CI, 3.03-3.52) for pulmonary embolism. After one year, the SIRs declined to 1.05 (95% CI, 0.96-1.16), 1.11 (95% CI 1.07-1.16) and 1.15 (95% CI, 1.09-1.22), respectively. For all three patient cohorts, particularly strong associations were found for cancers of the liver, lung, ovaries and pancreas as well as for non-Hodgkin's lymphoma. INTERPRETATION: Venous thrombosis, whenever it is seen in the lower limbs, is a preclinical marker of prevalent cancer, particularly during the first year after diagnosis.