Due to this large variety in results, we aimed to investigate the role of CYP2C19 genotypes on tamoxifen metabolism breast cancer survival outcomes in the large cohort of the prospective CYPTAM study32, which enrolled 667 Caucasian pre- and post-menopausal patients diagnosed with early-breast cancer receiving adjuvant tamoxifen. Here, CYP2C19 is linked to breast carcinoma.