The investigators want to research whether genetic polymorphisms of drug-metabolizing enzymes can be used to predict chemotherapeutic outcomes in patients with metastatic breast cancer.

1. Patients evaluation On all patients a complete clinical history and physical examination is performed, including routine hematology and biochemistry analyses. Hematology and biochemistry analyses are repeated at the end of each cycle. Toxicity is classified according to WHO criteria at each cycle for each patient. Response is assessed after two cycles of chemotherapy and every two cycles thereafter, using Response Evaluation Criteria in Solid Tumor Group (RECIST) guidelines.
2. Sample collection and SNP genotyping Venous blood (4 ml) is collected from each subject and placed into tubes containing EDTA. Genomic DNA is isolated with a DNA Blood isolation kit.Genotypes are performed by PCR-RFLP, PCR-DHPLC and PCR-direct sequencing, etc.
3. Statistical Analysis x2 test is used to summarize the association of response and adverse events to chemotherapy with genetic polymorphisms.

Inclusion Criteria:

• Histologically confirmed metastatic breast cancer
• Female
• An Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
• At least one measurable lesion
• Normal cardiac, hepatic, renal and bone marrow functions
• Life expectancy ≥3 months
• Discontinuity of previous chemotherapy for a minimum of 4 weeks

Exclusion Criteria:

• Central nervous system metastases
• Serious or uncontrolled concurrent medical illness
• History of other malignancies

female patients with metastatic breast cancer