Assessment of Clinical Risk Factors for Symptomatic Venous Thromboembolism in Common Cancers: A VERITY Registry Study

The association between venous thromboembolism (VTE) and cancer is well-recognised, but the thrombosis risk factor profile of patients with cancer-associated VTE is poorly characterised; it is unclear if additional risk factors contribute to the risk of thrombosis beyond the cancer itself, or if the risk factor profile is tumour-specific. Our aim was to compare the thrombosis risk factor profiles of cancer patients with or without symptomatic VTE enrolled in VERITY, an ongoing UK prospective VTE registry. The VERITY registry records data on patients with VTE and those in whom the diagnosis of VTE is excluded. Between Jun 05 and Mar 08, 49044 patient entries were made. Individual case data for patients with cancer were extracted. Using available risk factor data, univariate analysis of 9 established risk factors for VTE (medical in-patient history/immobilisation >3 days within last 4 weeks; major surgery in the last 4 weeks; hormonal risk factor; previous history of VTE; family history of VTE; known thrombophilia; intravenous drug abuse; current smoking; and leg paralysis), comparing VTE and non-VTE cancer cases, was performed for the 4 most common cancers using SPSS. To account for the potential impact of age and sex on VTE risk, age-adjusted values were calculated for breast and prostate cancer, and age- and sex-adjusted values for colorectal and lung. A nominal level of 5% statistical significance was assumed. Of 2825 cancer cases, 1382 had an objectively confirmed diagnosis of VTE and in 1443 the diagnosis of VTE was excluded. Breast (n=498), prostate (n=374), colorectal (n=343) and lung cancer (n=275) accounted for 53% of cancer cases. Univariate associations between risk factors and symptomatic VTE were found only for prostate cancer: history of VTE (odds ratio [OR] = 3.48; 95% CI, 2.01, 6.02; p < 0.00001), family history of VTE (OR = 2.56; 95% CI, 1.02, 6.44; p = 0.046), hormonal risk factor (OR = 2.22; 95% CI, 1.00, 4.92; p = 0.049). In colorectal cancer, smoking was less likely in VTE cases (OR = 0.54; 95% CI, 0.34, 0.87; p = 0.012). Adjusting for age (and sex), univariate associations between risk factors and symptomatic VTE were again found only for prostate cancer: history of VTE (OR = 3.23; 95% CI, 1.56, 6.68; p = 0.002), with smoking less likely in age-adjusted VTE cases (OR = 0.50; 95% CI, 0.28, 0.91; p = 0.022). Our analysis of a registry population found few associations between known thrombosis risk factors and symptomatic VTE in patients with common cancers, suggesting these factors impact little on thromboembolic risk in these cancers.