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

Abstract

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.