Postmenopausal women contemplating tamoxifen as part of their adjuvant hormonal therapy should consider testing for polymorphisms in CYP2D6.

Who should not consider testing at this time?

Perimenopausal and premenopausal women with hormone-positive breast cancer should not consider testing at this time. The current standard of care for these patients includes tamoxifen. If tamoxifen were omitted from their treatment plan, ovarian suppression by surgical oophorectomy or with a GnRH agonist (such as lupron) with or without the addition of an aromatase inhibitor, would be the only alternative. This therapy is currently being evaluated in the premenopausal setting as part of The Soft Trial* but has not yet been shown to be more effective than tamoxifen alone. In addition, early menopause has significant side effects, ranging from an increased risk of osteoporosis to hot flashes and changes in libido.

* The Soft Trial is evaluating tamoxifen versus ovarian suppression + tamoxifen versus ovarian suppression + aromatase inhibitor.