Endocrine Therapy Base on 21-gene RS

Among patients aged ≤50 years with hormone receptor-positive, HER2-negative breast cancer and pathologic nodal stage pN0-1-limited to those with an Oncotype DX® Recurrence Score (RS) of 11-25 for pN0 and ≤25 for pN1-, we will investigate the followings: i) Real-world patterns of adjuvant therapy (systemic chemotherapy and endocrine therapy) and radiotherapy according to N stage and Oncotype DX® RS. ii) Clinicopathologic characteristics of each patient subgroup by adjuvant treatment modality and RS category. iii) Survival outcomes and independent prognostic factors according to RS. iv) Survival analyses by adjuvant treatment modality, stratified by RS category, clinical risk, and N stage. Through these analyses, we aim to establish clinical evidence on whether endocrine therapy combined with ovarian function suppression (OFS) can substitute for adjuvant chemotherapy in HR+/HER2- patients with pN0-1 disease within the above RS ranges, and-if so-to define the patient subsets for whom this substitution is appropriate.