Gemcitabine plus cisplatin has been proved to be an effective regimen as second-line treatment for metastatic breast cancer patients, especially for those previously treated with anthracyclines and taxanes. Lobaplatin, as the third generation of new cancer drug platinum, has a similar anticancer activity to cisplatin, but less kidney toxicity and gastrointestinal reaction. The purpose of the study is to compare the efficacy and safety of gemcitabine/lobaplatin versus gemcitabine/cisplatin in patients with metastatic breast cancer.

Inclusion Criteria:

• Histologically confirmed metastatic breast cancer
• Disease progression during or after previous 1st line chemotherapy
• Scheduled to receive 2nd line chemotherapy.
• Measurable disease, defined as a least one lesion that can be accurately measured in at least one dimension
• 18 years of age or older
• ECOG performance status of 0-2
• Life expectancy of greater than 6 months

Exclusion Criteria:

• Previous treatment with one of the study drugs
• Application of other cytotoxic chemotherapy or radiotherapy
• Insufficent renal function (creatinine clearance < 60ml/min)
• Clinically unstable brain metastasis
• Pregancy or lactation
• History of other malignancy within last 5 years.