Factor V Leiden mutation increases the risk for venous thromboembolism in cancer patients - results from the Vienna Cancer And Thrombosis Study (CATS).

BACKGROUND: Patients with cancer are at an increased risk for venous thromboembolism (VTE). The risk varies markedly in different patient populations. Factor V (FV) Leiden is the most common genetic risk factor for VTE, and the impact of FV Leiden on cancer-associated thrombosis is not yet fully elucidated.
OBJECTIVE: To study the impact of FV Leiden on the risk of thrombosis in cancer patients.
METHODS: In the prospective observational Vienna Cancer And Thrombosis Study (CATS), 982 patients were included and were followed until occurrence of VTE or death, for a maximum period of 2 years. FV Leiden was determined by genotyping at inclusion. Main outcome measures were symptomatic or lethal objectively confirmed VTE.
RESULTS: Of the 982 patients, FV Leiden was diagnosed in 72 (7.3%, 70 were heterozygous and 2 were homozygous). Ten of 72 (13.9%) patients with FV Leiden developed VTE, whereas this was the case in 69 of 910 (7.6%) patients without FV Leiden. In multivariate analysis that included age, sex, different tumor types, tumor stage, newly diagnosed vs. recurrence of disease, and the treatment modalities, the hazard ratio was 2.0 (95% confidence interval 1.0-4.0). In Kaplan-Meier analysis, the probability for development of VTE was 13% in those with and 5.7% in those without FV Leiden after 6 months; after 1 year, the corresponding risks were 15% and 7.3%.
CONCLUSIONS: FV Leiden is a genetically determined and thus disease-independent parameter, which is associated with VTE in cancer patients and could therefore be used for individual risk assignment.