This study is a single-center, bidirectional cohort study. It aims to include 35 elderly (≥65 years old) Luminal A type breast cancer patients with axillary lymph node metastasis after surgery as the research subjects. After signing the informed consent, the patients who meet the inclusion criteria will have their various clinical and pathological data collected (preoperative imaging examinations, clinical and pathological information of the patients, basic disease conditions and medication strategies, surgical records, postoperative planned treatment plans and actual treatment situations, etc.), and their real adjuvant treatment situations (whether chemotherapy, radiotherapy, endocrine therapy, targeted therapy, etc. were performed after surgery) will be followed up and recorded. At the same time, paraffin tissues of breast cancer and metastatic lymph nodes of the patients will be collected from the pathology department of our hospital for 21-gene assay, and the recurrence risk index of the primary lesion and metastatic lymph nodes will be obtained using the risk index calculation logic of Amoy Diagnostics Company. An assessment will be conducted every 12 months after surgery until disease recurrence. After disease recurrence, survival follow-up will be conducted every three months until the patient's death. The predictive value of 21-gene assay for patient survival and whether chemotherapy is beneficial will be evaluated based on the follow-up data of the patients.