The investigator conduct a phase II multi-center, open-label trial to evaluate efficacy and safety of dalpiciclib with endocrine therapy as adjuvant treatment in patients with medium /high risk hormone receptor-positive, HER2-negative Early Breast Cancer.

Inclusion Criteria:

• Patient is ≥ 18 years-old
• Patient is female with known menopausal status (postmenopausal or premenopausal/perimenopause)
• Patient with histologically confirmed HR+/HER2- early breast cancer (immunohistochemical ER and/or PR≥10%)
• Histologically confirmed invasive breast cancer with anatomic stages of IIA-IIIC stage (T2-4N0-3M0), of which stage IIA only included T1N1M0
• Patients with or without neoadjuvant or adjuvant chemotherapy/ radiotherapy were eligible for inclusion
• From operation to enrollment should not exceed 12 months
• Patient has an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1

Exclusion Criteria:

• metastatic disease (Stage IV) or inflammatory breast cancer
• Previous or current history of malignant neoplasms, except for curatively treated:Basal and squamous cell carcinoma of the skin,Carcinoma in situ of the cervix.
• Clinically relevant cardiovascular disease:Known history of uncontrolled or symptomatic angina, clinically significant arrhythmias, congestive heart failure, transmural myocardial infarction, uncontrolled hypertension ≥180/110);
• A history of allergy to the drugs in this study；
• Unable or unwilling to swallow tablets
• History of gastrointestinal disease with diarrhea as the major symptom.