Vinorelbine Versus Gemcitabine Plus Vinorelbine in Metastatic Breast Cancer Patients

Inclusion Criteria:

* Histological or cytological diagnoses of breast cancer, with metastases.
* Metastatic lesions should not be curable with surgery or radiotherapy.
* Women of age \> 18.
* To have received a previous treatment with anthracyclines and taxanes.
* A maximum of 2 previous chemotherapy treatment lines for metastatic disease.
* Previous radiotherapy is allowed, whenever the radiated area is not the only disease location.
* At least 4 weeks since the last previous antineoplastic treatment; patient must have recovered from all previous toxicities.
* Performance status \< 2 in World Health Organization (WHO) scale.
* Clinically measurable, non measurable or really non measurable disease, as per Response Evaluation Criteria in Solid Tumors (RECIST) criteria.
* Life expectancy of at least 12 weeks.
* Patients able to comply and to receive an adequate follow-up.
* Adequate bone marrow function: neutrophils ≥ 2 x 10\^9/L; platelets ≥ 100 x 10\^9/L; hemoglobin ≥ 100 g/L.
* Calcium within normal limits.
* Premenopausal women must adopt an adequate contraceptive method during the study and up to 3 months after treatment finalization.

Exclusion Criteria:

* Active infection or serious concomitant disease (investigator's criteria).
* Clinical evidence of metastases in the central nervous system (CNS).
* Blastic bone lesions as only disease.
* Previous neurological toxicity grade 3-4 National Cancer Institute (NCI) Common Toxicity Criteria (CTC) v.2.0.
* Previous treatment with gemcitabine and/or vinorelbine.
* More than 2 previous chemotherapy treatment lines for metastatic disease.
* Abnormal liver function (bilirubin \> 2.0-fold upper normal limit (UNL); alanine transaminase (ALT) and aspartate transaminase (AST) \>2.5-fold UNL). In patients with hepatic metastasis, a value of ALT and AST of up to 5-fold UNL is permitted.
* Unpaired renal function (creatinine \> 2.0 mg/dL).
* Pregnancy or lactating.
* Treatment with any investigational agent in the previous 4 weeks.
* Second malignancy (except for cervix carcinoma in situ or skin carcinoma - no melanoma- with an adequate treatment). Previous malignancies are allowed if disease-free survival is superior to 5 years, except for renal carcinoma or melanoma.
* Males.