Inclusion Criteria:

- Provision of written informed consent

- Histologically or cytologically confirmed breast cancer

- Metastatic breast cancer (stage IIIB and IV). EGFR and/or HER-2 expression on the
primary tumor is not mandatory.

- Patients should have received at least one course of standard systemic chemotherapy
for their metastatic disease. Prior hormonal therapy is allowed.

- Patients should have achieved objective response (CR or PR) or stable disease to
previous first or second line treatment.

- There should be at least one month between the end of chemotherapy treatment and
trial entry. In case of prior Herceptin administration, 3 months are required to have
elapsed before study entry.

- Detection of ≥5 cells/7.5ml of peripheral blood detected by Cell Search System
despite the previous administration of chemotherapy and/or hormonal therapy.

- HER-2 expression on CTCs.

- Age 18 years and over

- Adequate Haematological function, Absolute neutrophil count ≥1.5 x 109/L, Platelet
count ≥100 x 109/L and Haemoglobin ≥9 g/dL (may be transfused to maintain or exceed
this level)

- Adequate Liver Function, total bilirubin <1.5 x upper limit of normal, AST and ALT
<2.5 x upper limit of normal in patients without liver metastases and <5 x upper
limit of normal in patients with liver metastases

- Adequate Renal function, Serum creatinine ≤1.25 x upper limit of normal or
calculated creatinine clearance ≥50 mL/min

- LVEF within institutional normal range

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2

- Life expectancy of at least 12 weeks

Exclusion Criteria:

- Any concurrent systemic treatment for breast cancer (including chemotherapy,
radiotherapy, hormonotherapy, monoclonal antibodies)

- Other co-existing malignancies or malignancies diagnosed within the last 5 years with
the exception of basal cell carcinoma or cervical cancer in situ

- Any unresolved chronic toxicity greater than Grade 2 (NCI- CTCAE) from previous
anticancer therapy (except alopecia)

- Any evidence of severe or uncontrolled systemic disease (e.g., unstable or
uncompensated respiratory, cardiac, hepatic, or renal disease)

- Pregnancy or breast feeding (women of child-bearing potential). Women of childbearing
potential must practice acceptable methods of birth control to prevent pregnancy

- Treatment with any other investigational agent, or participation in another clinical
trial within 28 days prior to enrolment

- Known hypersensitivity to drugs chemically related to lapatinib

- Concomitant requirement for medication classified as CYP3A4 inducers or inhibitors

- Evidence of any other disease, neurological or metabolic dysfunction, physical
examination finding or laboratory finding giving reasonable suspicion of a disease or
condition that contraindicates the use of an investigational drug or puts the patient
at high risk for treatment-related complications