Correlation of the tamoxifen use with the increased risk of deep vein thrombosis and pulmonary embolism in elderly women with breast cancer: A case–control study

The association between tamoxifen use and risk of deep vein thrombosis or pulmonary embolism in women with breast cancer has been reported in the Western population. The study aimed to evaluate the association between tamoxifen use and deep vein thrombosis or pulmonary embolism in older women with breast cancer in Taiwan. We conducted a retrospective case–control study using the database of the Taiwan National Health Insurance Program. A total of 281 women subjects with breast cancer aged ≥65 years with newly diagnosed deep vein thrombosis/or pulmonary embolism from 2000 to 2011 were identified as the cases. Additionally, 907 women subjects with breast cancer aged ≥65 years without deep vein thrombosis or pulmonary embolism were randomly selected as the controls. The cases and the controls were matched with age and comorbidities. Ever use of tamoxifen was defined as subjects who had at least a prescription for tamoxifen before index date. Never use of tamoxifen was defined as subjects who never had a prescription for tamoxifen before index date. We used the multivariable logistic regression model to calculate the odds ratio (OR) and the 95% confidence interval (CI) of deep vein thrombosis or pulmonary embolism associated with tamoxifen use. After adjustment for confounding variables, the adjusted OR of deep vein thrombosis or pulmonary embolism was 1.95 for subjects with ever use of tamoxifen (95% CI 1.45, 2.62), as compared with never use of tamoxifen. In addition, atrial fibrillation (adjusted OR 3.73, 95% CI 1.89, 7.35) and chronic kidney disease (adjusted OR 1.72, 95% CI 1.06, 2.80) were also associated with deep vein thrombosis or pulmonary embolism. Tamoxifen use is associated with 1.95-fold increased odds of deep vein thrombosis or pulmonary embolism among older women with breast cancer in Taiwan.