Efficacy and Safety of Fluzoparib Combined With Adjuvant Endocrine Therapy for HR+/HER2- SNF3-subtype Early Breast Cancer (BCTOP-L-A01)

Inclusion criteria

• 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.

Exclusion criteria

• Has bilateral breast cancer;
• Has previous history of additional malignancy, with the exception of adequately treated basal cell carcinoma and cervical carcinoma in situ.
• Has metastatic (Stage 4) breast cancer;
• Is pregnant, is breast feeding women, or women of childbearing age who cannot practice effective contraceptives;
• Patients participating in other clinical trials at the same time;
• Has severe organ dysfunction (cardiopulmonary liver and kidney) insufficiency, left ventricular ejection fraction (LVEF) \< 50% (cardiac ultrasound); severe cardio cerebral vascular disease within the 6 months previous of randomization (such as unstable angina, chronic heart failure, uncontrolled hypertension with blood pressure\>150/90mmgh, myocardial infarction, or cerebral blood vessel); diabetic patients with poor blood glucose control; patients with severe hypertension;
• Has known allergy to fluzoparib and excipients.
• Has severe or uncontrolled infection;
• Has a history of psychotropic substance abuse and were unable to abandon drug habits, or those with history of mental disorders;
• The researchers judged patients to be unsuitable for the study.