Factor V Leiden Mutation Increases the Risk of Venous Thromboembolism in Cancer Patients – Results From the Vienna Cancer and Thrombosis Study (CATS).

Patients with cancer are at an increased risk of venous thromboembolism (VTE). The risk varies markedly in different patient populations and improvement of the prediction of VTE would be of advantage for tailoring thrombosis prophylaxis. Factor V Leiden is the most common genetic risk factor for VTE and the impact of factor V Leiden on cancer-associated thrombosis is not yet fully elucidated.

To study the impact of factor V Leiden on the risk of VTE in cancer patients.

Nine-hundred-eighty-two patients with newly diagnosed cancer (n=745) or progression of disease after complete or partial remission (n=237) were included in the cancer and thrombosis study (CATS), a prospective observational single centre cohort study at the Medical University Vienna. Patients were followed for a maximum period of 2 years. Blood samples were collected at inclusion and factor V Leiden was determined by genotyping. The main outcome measure was symptomatic or lethal objectively confirmed VTE. All VTE events were adjudicated independently.

Of the 982 patients (median age 62 years, interquartile range (IQR) 52–68, 537 men, 445 women) factor V-Leiden was found in 72 (7.3%), 70 had a heterozygous and two a homozygous genotype. Ten of 72 (14%) patients with factor V-Leiden developed VTE, whereas this was the case in 69 of 910 (7.6%) patients without factor V-Leiden. Interestingly, both patients with homozygous factor V Leiden developed VTE. In multivariable analysis that included age, sex, different tumour types, newly diagnosed versus recurrence of disease and the treatment modalities (chemotherapy, radiotherapy and surgery) the hazard ratio (HR) for factor V Leiden was 2.04 (95% confidence interval (CI) 1.04–3.97)). In patients with newly diagnosed tumours the HR for factor V Leiden was 3.7 (95% CI 1.2–12.2) after 30 days. In Kaplan Meier analysis the probability for development of VTE after 6 months was 5.7% in those without and 13% in those with factor V Leiden, after one year the corresponding rates were 7.3% and 15%.

Factor V Leiden is a genetically determined and thus disease-independent parameter, which is associated with VTE in cancer patients, especially shortly after cancer diagnosis, and could therefore be used for individual risk assignment.

No relevant conflicts of interest to declare.