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-Common Toxicity
Criteria [NCI-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); ALT and 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.