Docetaxel and Cisplatin Chemotherapy With or Without High Dose Proton Pump Inhibitor in Metastatic Breast Cancer

Inclusion Criteria:

* Signed informed consent.
* Female, ≥ 18 years.
* Histologically confirmed invasive breast cancer.
* Metastatic breast cancer.
* Karnofsky Performance Status ≥60.
* Life expectancy of more than 3 months.
* Subject must have adequate organ function.
* Normal laboratory values: hemoglobin \> 80g/dl, neutrophils \> 2.0×10\^9/L, platelets \> 80×10\^9/L, serum creatinine \< upper limit of normal (ULN), serum bilirubin \< ULN, ALT and AST \< 2.5×ULN, AKP \< 5×ULN.
* Negative serum pregnancy test for women with childbearing potential.
* Good conditions for infusion and willing to have phlebotomy throughout whole study.
* Have ceased anti-tumor treatments including endocrinotherapy and bio-targeted therapy for more than 28 days.
* Have at least one target lesion according to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria.
* No prior use of docetaxel or has used docetaxel in adjuvant/neo-adjuvant chemotherapy and has a relapse free survival of at least 12 months.

Exclusion Criteria:

* Pregnant or lactating females.
* History of other malignancy. However, subjects who have been disease-free for 5 years, or subjects with a history of completely resected non-melanoma skin cancer or successfully treated in situ carcinoma are eligible.
* Concurrent disease or condition that would make the subject inappropriate for study participation, or any serious medical disorder that would interfere with the subject's safety.
* Active or uncontrolled infection.
* Known history of uncontrolled or symptomatic angina, arrhythmias, or congestive heart failure.
* Concomitant with brain metastases.
* Have received chemotherapy after metastasis.