The Risk of Malignancy Following Idiopathic Venous Thromboembolism: A Population-Based Cohort Study

Venous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), can be the earliest manifestation of an occult malignancy.

We used the hospital discharge (MED ECHO) database of the province of Quebec, Canada to determine the risk of a new cancer diagnosis in patients with idiopathic VTE.

Using data from Med-Echo which systematically records information on all hospital admissions in Quebec, we constructed a cohort of all individuals with a first-time diagnosis of DVT or PE between January 1, 1996 and December 31, 2004 and no cancer diagnosis preceding the VTE. Subjects were excluded if there was a surgical procedure, pregnancy, trauma or hospitalization in the 3 months prior to the VTE. Subjects were followed for 12 months after VTE for a first diagnosis of cancer (except non-melanoma skin cancer). VTE and cancer were defined using the 9^th edition International Classification of Diseases codes.

In all, 20 740 patients with idiopathic VTE and without previous cancer were identified. The mean age was 65.9 years (SD 12.6) and 58% were female. Overall, 696 (3.4%) patients were diagnosed with cancer in the 12 months following VTE. The risk was lowest among subjects aged 50 years or less (1.0%) and highest among patients aged 80 years or more (5.5%). Lung (25%) and gastrointestinal tumours (21%) were the most common diagnoses.

In this large population of patients with idiopathic VTE we found that 3.4% of patients were diagnosed with cancer in the first year following VTE, and that older patients had a higher risk of cancer compared to younger patients. This risk is less than previously reported estimates of 4–12%. The value of occult cancer screening in patients with idiopathic VTE is uncertain.

Tagalakis:Sanofi Aventis: Research Funding; Pfizer: Research Funding.