Background: Although cancer has been clearly associated with venous thromboembolism (VTE), many aspects of this relation are poorly understood, including the cancer sites most affected and the cancer risk during long-term follow-up. To clarify these relations, we carried out a large, population-based analysis of VTE and cancer risk.
Methods: Using the Swedish Inpatient Register and linkage to the nationwide Cancer Registry, we assessed cancer incidence during 1989 among 61,998 patients without a previous cancer diagnosis admitted to hospital between 1965 and 1983 for VTE. To measure possible increases in cancer risk, we computed standardised incidence ratios (SIRs) using Swedish national cancer rates for the period of the study.
Findings: At the time of thromboembolic admission or during the first year of follow-up, 2509 cancers were diagnosed (SIR 4.4, 95% CI 4.2-4.6) [corrected]. The SIR for polycythaemia vera was 12.9 (8.6-18.7), and the SIRs for cancers of the liver, pancreas, ovary, and brain, and for Hodgkin lymphoma also exceeded 5.0. Patients aged less than 65 years had higher SIRs than those who were older. In subsequent years, 6081 cancers were diagnosed (1.3, 1.3-1.3). Even 10 years or more after admission to hospital with VTE, cancer incidence had increased (1.3, 1.3-1.4).
Interpretation: At the time of VTE or in the first year afterwards, we found a large increase in the risk for diagnosis of virtually all cancers. In subsequent years, a persistent 30% increase in risk remains. Either premalignant change promotes thrombosis, or cancer and thrombosis share common risk factors.