Genotype-guided adjuvant endocrine therapy: new tricks from an old drug?

Evaluation of: Schroth W, Antoniadou L, Fritz P et al. Breast cancer treatment outcome with adjuvant tamoxifen relative to patient Cyp2D6 and Cyp2c19 genotypes. J. Clin. Oncol. 25, 5187-5193 (2007). Tamoxifen is one of the most commonly used treatments for breast cancer but is not effective in all patients. We review the study by Schroth and colleagues, evaluating the correlation between genotype for CYP2D6 and other enzymes involved in tamoxifen metabolism and breast cancer outcome. This study demonstrates that patients treated with tamoxifen with intermediate and poor metabolism genotypes have a higher risk of relapse, independent of other prognostic factors. Patients who were not treated with tamoxifen had no differences in outcomes based on CYP2D6 status. This study adds to the growing body of literature suggesting that genetic differences in patients can determine the effectiveness of tamoxifen and highlights the need for studies evaluating how genotype can best guide selection of endocrine therapy for breast cancer.