How do you manage endocrine therapy for premenopausal women with breast cancer who are heterozygous for factor V Leiden but have no history of thrombosis?  

This is a difficult situation given that the literature is contradictory on this topic. Both tamoxifen and a factor V Leiden mutation independently increase risk of thromboembolic events. It is unclear whether, together, they would be additive in conferring risk of thrombosis. Dr. Cuzick wrote a ve...