21-gene in Elder Breast Cancer Patients With Lymph Node Metastasis

Inclusion Criteria: * Sign a written informed consent； * Female, age ≥ 65 years old； * Patients who have undergone radical surgery for breast cancer (radical surgery refers to modified radical mastectomy, radical mastectomy or simple mastectomy + axillary lymph node dissection), and have been histologically confirmed to have axillary lymph node metastasis after surgery； * Postoperative immunohistochemical typing and pTNM staging meet the following criteria: 1. Luminal A type (ER and PR positive with a positive rate ≥ 20%, Her-2 gene negative, Ki67 \< 15%), with pTNM staging of pTanyNanyM0. 2. Or Luminal B, Her-2 gene negative type, with ER and PR positive and a positive rate ≥ 20%, Ki67 ≤ 30%, and pTNM staging of pTanyN1M0. 3. Or age ≥ 70 years old, Luminal B, Her-2 gene negative type, with ER and PR positive and a positive rate ≥ 20%, Ki67 ≤ 30%, and pTNM staging of pTanyNanyM0. 4. Or age ≥ 70 years old, but refuse or are unable to tolerate chemotherapy treatment, ER or PR positive, with pTNM staging of pTanyNanyM0； * ECOG score 0-1； * Expected survival time \> 6 months. Exclusion Criteria: * Patients who have received preoperative neoadjuvant therapy in the past; * Patients with bilateral breast cancer; * Patients whose paraffin tissue specimens have been stored for more than 3 years at the start of the project; * Patients with mental disorders who are unable to cooperate with subsequent treatment and follow-up; * Patients with a history or evidence of disease, treatment or abnormal laboratory test values that may interfere with the trial results or prevent full participation in the study, or other situations deemed unsuitable for inclusion by the researcher, or those considered to have other potential risks and thus not suitable for participation in this study.