* Among ER+HER2- premenopausal patients with N1 who undergoes primary breast surgery, we will identify the patients with a genomic low risk using the multigene-assay (OncoFREE®).
* In these, ovarian function suppression (OFS) with endocrine therapies including either tamoxifen or aromatase-inhibitors will be administered for 5 years.
* Either goserelin acetate or leuprorelin Acetate is allowed.
* These patients are able to choose bilateral salpingo-oophorectomy instead of OFS.
* Chemotherapy is omitted in these patients.
