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

Abstract

Abstract 5255 Background:Venous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), can be the earliest manifestation of an occult malignancy. Objectives: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. Methods: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 9th edition International Classification of Diseases codes. Results: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. Conclusions: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. Disclosures:Tagalakis:Sanofi Aventis: Research Funding; Pfizer: Research Funding.