The Clinical and Economic Impact of Pharmacogenomic Testing for Tamoxifen Metabolism in Postmenopausal Women Receiving Tamoxifen for Prevention of Recurrent Breast Cancer

Inclusion Criteria:

* Patient currently has a pharmacy benefit with Medco for an enrolled client
* Patient has a adjudicated tamoxifen pharmacy claims within the last six months
* Patient is still taking tamoxifen to prevent recurrent breast cancer
* Patient is a natural postmenopausal women 50 years of age or older
* Patient signs consent
* Patient is willing to provide sample for genetic testing
* Physician managing tamoxifen therapy is willing to order pharmacogenetic test

Exclusion Criteria:

* Patient is male
* Patient is under 50 years old
* Patient has previous history of CYP450 2D6 testing
* Patient is no longer taking tamoxifen
* Patient refuses to sign consent
* Patient wishes to no longer participate after testing
* Patient's physician refuses to order pharmacogenetic test