Past tamoxifen exposure was not materially associated with an elevated risk of developing VTE, and we therefore combined never and past users as reference group. High body mass index was an independent predictor of VTE itself. Our study provides evidence that current use of tamoxifen increases the risk of idiopathic venous thromboembolism. Doctors and scientists on the panel are worried that the drug might be used by women with only a slightly increased risk of developing breast cancer who do not understand tamoxifen's considerable risks. Tamoxifen-associated venous thrombosis and activated protein C resistance due to factor V Leiden.
Thromboembolic events are well recognized complications of cancers and their treatment.
Tamoxifen, an antiestrogen used in the treatment of breast carcinoma and other malignancies, has been associated with thrombotic events. Activated protein C resistance due to Factor V Leiden is the most prevalent inherited prothrombotic defect in populations of European descent and has been reported as a major cofactor in the development of thrombosis in women receiving estrogens. The authors report three patients who developed thromboembolic complications while receiving tamoxifen. These patients were studied for the presence of activated protein C resistance by coagulation assay and the presence of Factor V Leiden by molecular analysis. All three patients had resistance to activated protein C by coagulation assay and were determined to be heterozygous for Factor V Leiden by molecular analysis.