Olaparib in the Treatment of BRCA1/2 Unmutated and BRCA1 Promoter Methylated Recurrent and Metastatic Triple-negative Breast Cancer

Inclusion Criteria: * 1\. Age 18-70 years old, female; 2. Histologically confirmed recurrent and metastatic TNBC patients without BRCA1/2 mutation and BRCA1 promoter methylation. Note: Triple-negative breast cancer is defined as estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor (HER2) negative. ER and PR negative were defined as: ER\<1% positive, PR\<1% positive. HER2 negativity was defined as: HER2 (-) or (1+) or HER2 (2+) FISH negative by immunohistochemistry. 3\. The number of treatment lines at the stage of recurrence and metastasis should not exceed 2 lines. 4\. According to RECIST1.1 criteria, there is at least one evaluable lesion; 5. ECOG physical condition score ≤ 1 point; 6. Expected survival period ≥ 3 months; Exclusion Criteria: * 1\. Pregnant, breastfeeding women, or those who are fertile and unwilling to take effective contraceptive measures; 2. Patients who have received chemotherapy, radiotherapy, targeted therapy and other anti-tumor treatments within 4 weeks before enrollment; 3. Previous use of PARP inhibitors, including olaparib and other PARP inhibitors; 4. Known serious cardiovascular disease, myocardial infarction, or arterial thrombosis, or unstable angina pectoris, or known heart failure in the past 6 months, QT interval\>450ms; 5. The toxicity of the previous treatment regimen has not recovered before enrollment, and there are still toxic reactions of grade 1 or above (except for alopecia); 6. Clinic…