Prospective multicenter observational study to assess molecular drivers of metastatic breast cancer and disease evolution upon therapeutic pressure.

The main aim is to develop and validate prognostic, predictive and pathogenic markers in clinically well-characterized population-based material of breast cancer tumors and the corresponding normal tissue.These data will be used to characterize recurrent breast cancer on a molecular level, study tumor evolution, develop biomarkers of response/resistance to targeted therapy in the metastatic setting, enroll patients on targeted treatment clinical studies and to elucidate mechanisms of resistance to therapy.

Inclusion Criteria:

1. Patients with pathologically confirmed advanced breast cancer (ABC), including locally advanced inoperable disease and stage IV disease.
2. Age > 18 years.
3. Performance status according to Eastern Cooperative Oncology Group (ECOG) ≤ 2.
4. ABC must be radiologically or clinically assessable, by means of at least one of the following techniques: clinical examination, computerized tomography (CT-scan), magnetic resonance imaging (MRI), bone scintigraphy or positron emission tomography (PET).
5. Patients must have a radiological evaluation done maximum 6 weeks prior to inclusion.
6. Signed informed consent according to ICH/GCP, and national/local regulations.

Exclusion Criteria:

Untreated psychiatric disorders that will impair the patient's ability to comply with study treatment or protocol.

Patients diagnosed with metastatic, inoperable breast cancer.