Our study aims to evaluate the possibility of clinical application of CTDNA detection in samples or peripheral blood of breast cancer patients, so as to act as the new techniques or indicators of early diagnosis, therapy efficiency, or postoperative surveillance of breast cancer.

Inclusion Criteria:

1. Written informed consent must be obtained and documented according to the local regulatory requirements prior to beginning specific protocol procedures.
2. Age of at least 18 and at most 70 years.
3. Performance status (Karnofsky-Index) >80%.
4. Chemotherapy is necessary before or after surgery.
5. No clinical evidence of local recurrence or distant metastases.
6. Complete staging work-up within 3 months prior to registration. All patients must have (bilateral) mammography or breast MRI, chest X-ray; other tests may be performed as clinically indicated.
7. Life expectancy of at least 2 years, disregarding the diagnosis of cancer.
8. Adequate organ function including normal red and white blood count, platelets, serum creatinine, bilirubin, and transaminases within normal range of the institution.
9. Patients must be available for and compliant to treatment and follow-up.
10. Patients registered on this trial must be treated and followed up at the participating center.

Exclusion Criteria:

1. Known hypersensitivity reaction to the investigational compounds or incorporated substances.

2. Local recurrence and/or metastasis of breast cancer.

3. No need of chemotherapy.

4. Pregnant or lactating patients. Patients of childbearing potential must have a negative pregnancy test (urine or serum) within 14 days prior to registration.

   Prior or concomitant secondary malignancy (except non-melanomatous skin cancer or carcinoma in situ of the uterine cervix)

5. Any other serious medical pathology, such as congestive heart failure; unstable angina; history of myocardial infarction during the previous year; uncontrolled high risk arrhythmias

6. Other serious illness or medical condition that may interfere with the understanding and giving of informed consent and the conduct of the study.

7. Concurrent treatment with other experimental drugs or any other anti-cancer therapy.

8. Males.

Operable breast cancer patients who need chemotherapy before or after surgery.