Pharmacogenomics of Tamoxifen: Can Therapeutic Outcomes Be Tailor Made?

Efforts to tailor endocrine therapy for advanced or early-stage breast cancer began with the knowledge that tamoxifen's principal CYP2D6 metabolite, endoxifen, held its primary anticancer effect. Studies of tamoxifen's pharmacogenomics have characterized CYP2D6 genotypes and how therapeutic outcomes might vary based on degree of tamoxifen metabolism. Now, two reports add to this work.

In the first study, investigators used CYP2D6 genotyping data from two Swedish registries including 1300 women who received adjuvant tamoxifen to categorize patients as poor, intermediate, normal, or ultra-rapid CYP2D6 metabolizers. They hypothesized that prognoses would be worse not only in poor metabolizers (due to lower therapeutic concentrations of endoxife…