ESR1 and breast cancer: To address this question, we aimed to study the association among response (relapse and ADR) and 7 genetic variants in genes encoding proteins involved in the pharmacokinetics and pharmacodynamics of TAM (CYP2D6∗4, CYP3A4∗1B (CYP3A4∗1.001), CYP3A5∗3, SULT1A1∗2, UGT2B7∗2, UGT2B15∗2 and ESRA V364E) in women with hormone-dependent BC and under adjuvant treatment with TAM.