Cancer incidence and mortality after a first-ever venous thrombosis: a cohort study in northern Sweden.

Background: Venous thromboembolism (VTE) has a high mortality rate and can be the first manifestation of cancer. We investigated the incidence of cancer after first-ever VTE and the association between VTE and all-cause mortality.

Methods: A Swedish cohort study that included 105,997 participants without previous cancer who underwent a health examination from 1985-2014 was conducted. Manually validated first-ever VTE events, incident cancer according to the Swedish cancer registry, and mortality were registered. Participants were followed until September 5, 2014.

Results: The mean age at inclusion was 46.2 years, and 50.3% of participants were female. We identified 1303 persons in the cohort with a VTE and no previous cancer. Among these, 179 (13.7%) were diagnosed with cancer after the VTE event, resulting in a cancer incidence of 26.4 (95% CI 22.8-30.6) cases per 1000 person-years. The incidence was highest during the first 6 months after the VTE. In the study population, VTE was associated with an increased risk of cancer (HR 1.95 [95% CI 1.67-2.29] in a multivariable model). VTE was also associated with an increased risk of death (HR 6.30 [95% CI 5.82-6.81]) in a multivariable model). There was an interaction between sex and VTE in relation to both risk of cancer and mortality, with a stronger association in women.

Conclusions: The incidence of cancer is high after first-ever VTE, especially close to the VTE event. VTE seems to be a stronger risk marker in women than in men for both cancer and death.