The long-term risk of cancer in patients with a first episode of venous thromboembolism

Summary.  Background: In patients with venous thromboembolism (VTE), 15–20% will have prevalent cancer when VTE is diagnosed but little is known about such patients' long-term risk, time course and predictors of new cancer. Patients and methods: We studied an inception cohort of patients with a first VTE who were not diagnosed with cancer within 3 months after VTE and who had follow-up for up to 120 months. We determined the annual risk for a new cancer [number of events and 95% confidence interval (CI)] per 100 person-years in all patients and in those with unprovoked VTE and identified predictors for new cancer. Results: We studied 1852 patients with VTE who received anticoagulant therapy for 12 months (mean) and were followed for 4.2 years (mean). During follow-up, there were 105 (5.7%) patients diagnosed with new cancer during the period after the initial 3 months from diagnosis, for an annual risk of 1.32 (CI, 1.09–1.60) per 100 person-years. The risk for new cancer appeared uniform over time. The annual risk for new cancer was more than 2-fold higher in patients presenting with unprovoked compared with those with provoked VTE [1.76 (CI, 1.39–2.20) vs. 0.83 (CI, 0.58–1.16) per 100 person-years; P  < 0.001]. Clinical predictors for new cancer were increasing age [hazard ratio (HR), 1.23; CI, 1.05–1.44] and unprovoked VTE (HR, 1.86; CI, 1.21–2.87). Conclusion: In patients with a first VTE and without prevalent cancer, the risk for new cancer is about 1–2% per year, appears to be uniform over time, and is higher in patients with unprovoked VTE and those with advanced age.