This non-interventional study aims at assessing the impact of nab-paclitaxel on the clinical outcomes and the health-related QoL (HRQoL) of this heavily burdened and difficult-to-treat population. Notably, the data generated in the context of this study will serve as complementary evidence to that of the tightly and strictly controlled pre-registration clinical trial setting, which is of essential importance especially in patient populations with diseases of complex and heterogeneous biology, such as breast cancer.

Inclusion Criteria:

Patients eligible for inclusion in this study have to meet all of the following criteria:

• Adult patients (18 years and older);
• Patients with a histologically or cytologically confirmed diagnosis of MBC who have failed first-line treatment for metastatic disease and for whom standard, anthracycline containing therapy is not indicated;
• Patients for whom the decision to prescribe therapy with nab-paclitaxel according to the locally approved product's summary of product characteristics (SmPC) has already been taken prior to their enrolment in the study; the assignment of the patient to this therapeutic strategy is not decided in advance by the study protocol but falls within current practice and the prescription of nab-paclitaxel is clearly separated from the physician's decision to include the patient in the current study;
• Patients must be able and willing to provide written informed consent and to comply with the requirements of this study protocol;
• Patients must have signed an informed consent document;
• Patients must be able to read, understand and complete the study specific questionnaire

Exclusion Criteria:

A patient who meets any of the following criteria will be excluded from participation in this study:

• Patients who have initiated treatment with nab-paclitaxel more than 7 days prior to their enrolment into the study;
• Patients that meet any of the contraindications to the administration of the study drug according to the approved SmPC;
• Receipt of any investigational agent within 30 days or 5 half-lives of the investigational agent (whichever is longer) before the commencement of therapy with nab-paclitaxel.

Adult patients with a histologically or cytologically confirmed diagnosis of MBC who have failed first-line treatment for metastatic disease and for whom standard, anthracycline containing therapy is not indicated