Women with a diagnosis of hormone receptor‐positive breast cancer with an indication for adjuvant endocrine therapy, with no progress of disease or relapse, diagnosis of other current carcinoma, having received neo‐adjuvant chemotherapy, having a severe acute psychiatric disorder or a physical comorbidity substantially influencing quality of life, and starting endocrine therapy before baseline assessment or having pre‐experiences with endocrine therapy (four breast cancer centres in Marburg and Hamburg, Germany). This evidence concerns the gene NR4A1 and breast cancer.