The objectives of this study are to evaluate the efficacy and tolerability of high dose proton pump inhibitor combined with chemotherapy in metastatic breast cancer.

High dose proton pump inhibitor (PPI) has been proved beneficial and it improved efficacy when combined with chemotherapy in preclinical and clinical trials.This study was designed to explore whether adding a proton pump inhibitor into docetaxel and cisplatin chemotherapy improves efficacy and does not affect tolerability 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.