The cerebrovascular risks associated with tamoxifen use.

Tamoxifen, a selective oestrogen receptor modulator with oestrogen antagonistic effects in the breast, is an effective treatment for breast cancer. Although tamoxifen has been shown to have favourable effects on cardiovascular risk factors, several studies have shown an increased risk of venous thrombosis and stroke. The mechanisms of increased risk of both venous and arterial thrombosis remain unclear based on measurement of markers of thrombosis in women using tamoxifen. In addition, the aetiology of stroke, emphasising the distinction between cerebral venous thrombosis and ischaemic or haemorrhagic stroke, as well as paradoxical embolism, needs to be determined before the issue of stroke risk can be clarified. Future studies of women with breast cancer using tamoxifen should be designed to determine the stroke etiologies that are most common in women using tamoxifen, the role of additional chemotherapy and existing stroke risk factors, and the potential mechanisms of venous and arterial thrombosis.