A Phase III, Multicenter, Randomized, Double-blind, Placebo-controlled Study to Evaluate Efficacy and Safety of Ribociclib With Endocrine Therapy as an Adjuvant Treatment in Patients With Hormone Receptor-positive, HER2-negative, High Risk Early Breast Cancer

• Histologically confirmed unilateral primary invasive adenocarcinoma of the breast
• Estrogen receptor-positive and/or progesterone receptor-positive, HER2-negative breast cancer
• Patient is after surgical resection of the tumor where tumor was removed completely,
• Patient who received adjuvant chemotherapy and have AJCC 8th edition Prognostic Stage Group III tumor; or patient who received neoadjuvant chemotherapy and have 1 or more ipsilateral axillary lymph nodes with residual tumor metastases greater than 2.0 mm in lymph node(-s) and residual tumor greater than 10.0 mm in breast tissue
• Patient has completed multi-agent adjuvant or neoadjuvant chemotherapy of ≥ 4 cycles or ≥ 12 weeks which included taxanes prior to screening
• Patient has completed adjuvant radiotherapy (if indicated) prior to screening
• Patient may already have initiated adjuvant endocrine therapy (ET) at the time of randomization, but randomization must take place within 52 weeks of date of initial histological diagnosis of breast cancer and within 12 weeks of initiating ET
• ECOG PS 0-1
• No prior treatment with CDK4/6 inhibitor
• No prior treatment with tamoxifen, raloxifen or aromatase inhibitors for reduction in risk (chemoprevention) of breast cancer and/or treatment for osteoporosis within last 2 years
• No prior treatment with anthracyclines at cumulative doses of 450 mg/m² or more for doxorubicin
• No distant metastases of breast cancer beyond regional lymph nodes
• Uncontrolled hypertension with systolic blood pressure >160 mmHg

Primary- Invasive DFS;  Secondary- RFS, distant DFS, OS, QoL