The Efficacy and Safety of CDK4/6 Inhibitors in Combination with Endocrine Therapy in the Neoadjuvant Treatment

Inclusion Criteria: 1. Age ≥ 18 years old. 2. Premenopausal and postmenopausal stage II-III females or males (patients with multicenter and/or multifocal early-invasive breast cancer) if all histopathological examination of tumors meet the pathological criteria of ER and/or PR\>10% and HER2- (HER2 expression 0 or 1+ or 2+ and negative FISH test). 3. Patients must have histologically confirmed ER and/or PR \>10%, HER2-, early invasive breast cancer. 4. Intolerance or insensitivity to neoadjuvant chemotherapy: 2 cycles of neoadjuvant chemotherapy, tumor evaluation PD/SD, advanced age, and inability to tolerate chemotherapy with underlying diseases. 5. ECOG PS score 0-2. 6. Patients must be able and willing to swallow and retain oral medications. 7. Premenopausal women within 14 days of enrollment, or women with amenorrhea for less than 12 months at the time of enrollment, must have a negative serum or urine pregnancy test. 8. Patients who have received neoadjuvant endocrine therapy are eligible for enrollment as long as they are enrolled within 6 months of initial histologic diagnosis and have completed no more than 2 months of neoadjuvant endocrine therapy. 9. Absolute neutrophil count ≥ 1500/µL, platelet ≥ 100000/mm3, hemoglobin ≥ 10g/dL Exclusion Criteria: 1. Prior treatment with any CDK inhibitor. 2. Inflammatory breast cancer or stage IV breast cancer or bilateral breast cancer. 3. History of anaphylaxis caused by chemical or biologic components similar to dalsily. 4. Patients who have received any drugs or substances with effective CYP3A isoenzyme inhibitors or inducers within 7 days of enrollment. 5. Uncontrolled intercurrent illness that would limit compliance with study requirements. 6. Pregnant women or women of childbearing potential with a negative pregnancy test within 14 days prior to admission. 7. Patients with any history of malignancy are not eligible. 8. Patients who have received endocrine therapy within 5 years prior to the diagnosis of the current malignancy.