Familial risk factors shared by venous thromboembolism and cancer: A nationwide epidemiological study of Swedish families

Background: Cancer and venous thromboembolism (VTE) are associated disorders. In the present nationwide study, we analyzed the risk of cancer in siblings, offspring and spouses of individuals hospitalized for VTE (and vice versa) with the aim of identifying shared familial risk factors for cancer and VTE. Material and Methods: The Multigeneration Register was linked to the Swedish Hospital Discharge Register and the Swedish Cancer Registry. Associations between the familial risks for VTE and cancer were examined by measuring the risk of developing specific cancers in the offspring of individuals diagnosed with VTE, and the risk of VTE in the offspring of individuals diagnosed with specific cancers. The analysis was repeated for siblings and spouses. Results: No overall associations between cancer and VTE were observed in parent-offspring pairs. In contrast, the risk of cancer was slightly increased in siblings of VTE patients (OR 1.03, 95% CI 1.01-1.06), and the risk of VTE was also increased in siblings of cancer patients (OR 1.07, 95% CI 1.04-1.10). Risks of cancer were also slightly increased in the husbands (OR 1.09, 95% CI 1.07-1.11) and wives (OR 1.02, 95% 1.00-1.05) of individuals with VTE. Conclusion: The present study provides evidence for minor familial risk factors shared by VTE and common cancers. These could be mostly environmental because of the positive associations in the spouse and sibling analyses and negative associations in the parent-offspring analysis, although the possibility of shared genetic risk factors also exists.