Efficacy and Safety of CDK4/6 Inhibitors Combined With Endocrine Therapy in HR+/HER2- Neoadjuvant Therapy for Early Breast Cancer

Inclusion criteria

• 1. Age ≥18 years old.

• Premenopausal and postmenopausal women or men with stage II-III disease (multifocal and/or multifocal early invasive breast cancer) if all tumors on histopathological examination meet the pathological criteria for ER and/or PR > 10% and HER2- (HER2 expression of 0 or 1+ or 2+ and negative FISH test).

3.Patients had to have histologically confirmed ER and (or PR>10%, HER2 -, early-stage invasive disease.

4.Intolerance or insensitivity to neoadjuvant chemotherapy: 2 cycles of neoadjuvant chemotherapy, PD/SD according to tumor evaluation, old age, and basic diseases can not tolerate chemotherapy.

• ECOG PS score 0-2.

• Patients must be able and willing to swallow and retain oral medications.

• In premenopausal women, a serum or urine pregnancy test had to be negative within 14 days of enrollment or in women who had been amenorrhea for less than 12 months at enrollment.

8.Patients who had received neoadjuvant endocrine therapy were eligible if they were enrolled within 6 months of the initial histologic diagnosis and had completed no more than 2 months of neoadjuvant endocrine therapy.

• Absolute neutrophil count ≥1500/µL, platelet ≥100000/mm3, hemoglobin ≥10g/dL

Exclusion criteria

• 1. Prior treatment with any CDK4/6 inhibitor.

• Inflammatory or stage IV or bilateral breast cancer.

• History of allergic reactions caused by chemical or biological components similar to CDK4/6 inhibitors.

Patients who received any drugs or substances that were effective CYP3A isoenzyme inhibitors or inducers within 7 days of enrollment.

• Uncontrolled coexisting medical conditions may limit adherence to study requirements.

• Pregnant women with a negative pregnancy test within 14 days before admission or women of childbearing potential.

• Patients with a history of any malignancy were not eligible.

• Patients receiving endocrine therapy within 5 years before diagnosis of current malignancy.