Breast Cancer Clinical Trials

• Women aged 18-70 years old;

• ECOG score 0 or 1;

• ER+/HER2- confirmed by histopathology after early breast cancer surgery（ER positive is defined as immunohistochemistry(IHC) detection of ER ≥ 1% HER2-negative is defined as a negative in situ hybridization test or an IHC status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization (Fluorescence in situ hybridization (FISH), Chromogenic in situ hybridization (CISH) , or Silver in situ hybridization (SISH)) test is required by local laboratory testing.); definition of SNF3 subtype: SNF3 subtype confirmed by digital pathology of H\&E sections;

• Postoperative pathological stage T2-4N0-3M0;

• Patients who have previously received neoadjuvant chemotherapy and/or adjuvant chemotherapy;

• Time of randomization from surgery does not exceed 16 months;

• Time of endocrine therapy from last non-endocrine anti-tumor treatment does not exceed 12 weeks;

• Has adequate organ function meeting the following criteria: (1) adequate bone marrow function: hemoglobin ≥ 90 g/L (no blood transfusion within 14 days); absolute neutrophil count ≥ 1.5 x 10\^9 /L; platelet count ≥ 100 \* 10\^9 /L; (2)adequate liver and kidney function: Alanine Aminotransferase (ALT) ≤ 3×upper limit of normal (ULN), Aspartate Aminotransferase (AST) ≤ 3×ULN, Total Bilirubin (TBIL)≤ 1.5×ULN, serum creatinine ≤ 1×ULN，and with endogenous creatinine clearance rate of \>50 ml/min (Cockcroft-Gault formula);

• Patients receiving radiotherapy must recover from the acute phase reaction of radiotherapy, with a washout period of at least 14 days from the end of radiotherapy to randomization;

⁃ Patients who received chemotherapy in the early stage must recover from acute adverse reactions to chemotherapy (\[CTCAE\] grade ≤ 1) before randomization, except for hair loss or grade 2 peripheral neuropathy. There is a washout period of at least 21 days from the last chemotherapy administration to randomization (assuming the patient has not received radiotherapy);

⁃ Patients can take medication orally on their own;

⁃ Female subjects with fertility are required to use a medically approved contraceptive method during the study treatment

⁃ Participants voluntarily joined the study, has signed informed consent before any trial related activities are conducted, has good compliance and has agreed to follow-up.