This study is a prospective, multicenter non-interventional cohort study designed to develop a registry in unresectable locally advanced or metastatic disease.

The target population for inclusion in this study is breast cancer patients recently diagnosed (from January 2016) with unresectable locally advanced or metastatic disease (either after a recurrence or as first diagnosis). No treatment regimen will be protocol specified. This is an observational study in which clinical decisions concerning the optimum management strategy for a particular patient are taken independently of and/or prior to, any decision by the physician to invite a patient to participate in the study. The treating physician will make all treatment decisions according to his/her regular clinical practice independent of this study. Patients enrolled on the study are free to withdraw their informed consent for the use and disclosure of health information at any time and when asked, patients are not obliged to provide a reason. Patients may request discontinuation from the study at any time.

The date and the reason for withdrawal or discontinuation from the study must be recorded in the electronic case report form (eCRF). An attempt will be made to determine the date of discontinuation and final status (i. e. withdrawal of consent, loss to follow-up, death) of any patient who discontinues from the study. However, the treating clinician is encouraged to follow the patient as long as possible, until patient death or through study end. The Sponsor has the right to terminate the study at any time. The Sponsor will notify the investigator if the study is placed on hold or if the Sponsor decides to discontinue the study.

Inclusion Criteria:

1. Patients (males or females) diagnosed with unresectable locally advanced or MBC (either after a recurrence or as first diagnosis) from January 2016 onwards.
2. Patients who died are allowed to be included on the study.
3. Able and willing to provide written informed consent if they are alive.
4. Age ≥ 18 years.
5. Availability to medical records access and all data related to the disease management.

Exclusion Criteria:

None

The target population for inclusion in this study is breast cancer patients recently diagnosed (from January 2016) with unresectable locally advanced or metastatic disease (either after a recurrence or as first diagnosis).