Gene mutation increases clot risk in women on tamoxifen

Women taking adjuvant tamoxifen for early-stage breast cancer who develop a thromboembolism (TE) are nearly 5 times more likely to carry the factor V Leiden (FVL) mutation than women on the medication who don't have a TE, according to a study published online June 16 in the Journal of the National Cancer Institute, reported HealthDay News.

Judy E. Garber, MD, of the Dana-Farber Cancer Institute in Boston, and colleagues conducted a case-control study in which they matched each of 124 women who had a TE while taking tamoxifen to two control subjects who took tamoxifen without having a TE. The researchers analyzed the women's DNA from blood samples for the presence of the FVL mutation.

The researchers found that FVL mutations were present in 18.5% of the women experiencing TEs and 4.8% of the subjects without TEs. In multivariate analysis, the FVL mutation was associated with increased risk of TE (odds ratio, 4.73) compared with not having the mutation. A medical history of TE and smoking were also associated with increased TE risk.

"Among women taking adjuvant tamoxifen for early-stage breast cancer, those who had a TE were nearly 5 times more likely to carry a FVL mutation than those who did not have a TE. Postmenopausal women should be evaluated for the FVL mutation before prescription of adjuvant tamoxifen if a positive test would alter therapeutic decision making," the authors wrote.

One study author reported ties to AstraZeneca and Pfizer.