However, these data are contradictory to the previously published data of Hertz (2017), who performed a retrospective analysis of two community-based studies to assess for the associations between the low-activity CYP2D6 genotype and disease outcome in 500 breast cancer patients treated with adjuvant tamoxifen monotherapy, and 500 patients who did not receive any systemic adjuvant therapy. This evidence concerns the gene CYP2D6 and breast carcinoma.