Incidence of Venous Thromboembolism and the Impact on Survival in Breast Cancer Patients

PURPOSE: The incidence of venous thromboembolism (VTE) and the risk factors associated with development of VTE have not been reported in a large population-based study of breast cancer patients. PATIENTS AND METHODS: The California Cancer Registry was merged with the Patient Discharge Data Set, and the number of VTE events determined among patients diagnosed between 1993 and 1999. RESULTS: Among 108,255 patients with breast cancer, the 2-year cumulative VTE incidence was 1.2%, with a rate of 1.2 and 0.6 events/100 patient-years during the first and second half-year, respectively. The 1-year incidence of VTE was significantly increased compared with the general population (standardized incidence ratio of VTE, 4.2; 95% CI, 3.9 to 4.4). In a multivariate model, significant predictors of developing VTE within 2 years were: age (hazard ratio HR, 2.0 if > 75 years v < 45; 95% CI, 1.6 to 2.6), the number of chronic medical comorbidities (HR, 2.9 if 3 v 0; 95% CI, 2.4 to 3.5), and advancing cancer stage (HR, 6.3; 95% CI, 5.3 to 7.5 for metastatic v local disease). In multivariate models, VTE was a significant predictor of decreased 2-year survival (HR, 2.3; 95% CI, 2.1 to 2.6) and when stratified by initial cancer stage, the effect was highest in patients with localized (HR, 5.1; 95% CI, 3.6 to 7.1) or regional stage (HR, 3.5; 95% CI, 2.5 to 4.8) cancer compared with patients with metastatic disease (HR, 1.9; 95% CI, 1.5 to 2.4). CONCLUSION: Approximately 1% of breast cancer patients developed VTE within 2 years, with the highest incidence in the first 6 months after diagnosis. Metastatic disease and comorbidities were the strongest predictors. The diagnosis of VTE was associated with a higher risk of death within 2 years.