PROOFS-Registry - Premenopausal Women With Breast Cancer Optimally Treated With OFS

This registry aims * to confirm an excellent outcome in pre-/perimenopausal patients treated by endocrine therapy (+ ovarian suppression) in patients with low genomic risk by MammaPrint® without chemotherapy use in a real-world setting. * to evaluate management of ovarian function in patients treated by adjuvant chemotherapy according to investigator decision. * to evaluate adherence to endocrine therapy (+/- ovarian function suppression). * to evaluate the prognostic impact of clinicopathological markers (e.g., estrogen receptor (ER), progesterone receptor (PR), HER2 receptor, Ki-67 at baseline and after preoperative endocrine therapy (if any performed) by local pathology assessment compared to genomic signature result. * to assess the course of quality of life (QLQ BR23 and QLQ-C30) until 5 years of treatment with OFS (Baseline, 3 months, 6 months, 12 months, 18 months, 2 years, 3 years, 4 years, 5 years) In general, WSG aim to assess the quality of surveillance care in younger breast cancer patients. WSG want to gain knowledge about endocrine induction treatment for indication of chemotherapy followed by endocrine treatment or endocrine treatment alone. Also, WSG aim at changes in duration of endocrine treatment (especially in high-risk patients up to 10 years) and introduction of intensified endocrine therapy (OFS) in combination with GnRH-analogues since publication of the SOFT and TEXT trials.