A Multicenter, Open-label, Randomized Controlled Phase II Clinical Study of Ribociclib Combined with Aromatase Inhibitors (AI) Versus Chemotherapy Followed by Physician's Choice of Endocrine Therapy in Elderly Patients with Node-positive, Intermediate-to-high Risk HR+/HER2- Early Breast Cancer

INTERVENTION: A:Ribociclib + AI;B:Chemotherapy followed by physician's choice of endocrine therapy (AI +/‐ CDK4/6 inhibitors); CONDITION: Breast cancer PRIMARY OUTCOME: Invasive Disease‐Free Survival, iDFS; SECONDARY OUTCOME: Recurrence‐Free Survival, RFS;Distant Metastasis‐Free Survival, DMFS;Overall Survival, OS;Safety;Quality of Life, QoL; INCLUSION CRITERIA: 1. Age: Female patients >=65 years of age; 2. Diagnosis: Histologically confirmed HR+/HER2‐ early invasive breast cancer; 3. Risk Profile: Node‐positive, intermediate‐to‐high risk (according to UICC 8th Edition); 4. Performance Status: ECOG Performance Status of 0‐2; 5. Prior Treatment: Completion of radical surgery within 8 weeks prior to randomization; 6. Organ Function: Adequate organ and bone marrow function; 7. Informed Consent: Ability to understand and willingness to sign the written Informed Consent Form (ICF).