Inclusion Criteria

Inclusion criteria:

- Female patients with histologically proven breast adenocarcinoma

- Presence of metastatic disease No more than 2 prior chemotherapy regimens for
metastatic disease, which could include trastuzumab Patients must currently be on
letrozole and developed acquired resistance as defined by disease progression on
letrozole following previous response (partial response or better, stable disease
superior or equal to 24 weeks)

Diagnosis of disease progression inferior or equal to 6 weeks prior to trial entrydefined
as:

1. Increase in the number of bone lesions on bone scan or on MRI AND/OR

2. Increased pain in an area of known bony metastasis AND superior or equal to 2 serial
elevations in CA 15.3 AND/OR

3. Progression according to RECIST criteria on CT scan, MRI, or x-ray Patients must have
documented menopause confirmed by estradiol level inferior to 11 pg/ml

Exclusion criteria:

- Premenopausal patients

- Rapidly progressive disease in major organs (i.e. lymphangitic spread in the lung
and/or bulky liver metastasis) Patient with brain metastasis Significant
cardiovascular diseases Previous treatment with an EGFR and/or HER-2 inhibiting
drug(patients who received trastuzumab with chemotherapy but not with letrozole can
be enrolled)