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Use of tamoxifen to prevent breast cancer recurrences has long been associated with an increased risk of developing blood clots. It appears, however, that women who take tamoxifen and have the Factor V Leiden (FVL) genetic mutation may have an even higher risk of clots compared to women taking tamoxifen who do not carry this mutation. Factor V Leiden is the most common hereditary coagulation disorder. It affects approximately 5% of the Caucasian population.
A study of >300 women, conducted at Yale University School of Medicine, revealed that women who developed blood clots while on tamoxifen were 4 times as likely to carry the FVL mutation. The researchers concluded that their results suggest that testing women for FVL prior to adjuvant therapy may enable physicians to investigate alternatives to tamoxifen or prescribe blood thinners during treatment of women at high risk of clot development.
Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.