Tamoxifen is the gold-standard treatment for hormone-sensitive breast cancer. Scientists looked at 412 women who were administered tamoxifen after breast cancer surgery and found that those who developed blood clots were five time more likely to carry the Factor V Leiden (FVL) gene.
Previous studies have already shown that the drug doubles the risk of blood clots in women, overall. But in people with the FVL gene mutation its impact is even bigger, scientists said, raising the risk of conditions such as deep vein thrombosis and pulmonary embolism - a potentially life-threatening blood clot on the lung.
The mutation is inherited and is more prevalent among people with northern European and Scandinavian ancestry. It is present in around 5 per cent of the UK population.
'These data may prove useful to women who must decide between tamoxifen and an effective, essentially non-thrombogenic, alternative adjuvant therapy for breast cancer', wrote lead researcher Dr Judy Garber and her team.
Possible tamoxifen alternatives included aromatase inhibitors for post-menopausal women, and gonadotrophin-releasing hormone analogues for pre-menopausal women.
The research was published in the Journal of the National Cancer Institute.
Sources and References
Gene linked to blood clot danger
Gene linked to cancer therapy risk