Breast Cancer Registry Platform

Inclusion Criteria: EBC cohort: * Female and male patients with early breast cancer (stage I-III defined as breast cancer that has not spread beyond the breast or the axillary lymph nodes) * Patients at the start of their initial systemic treatment for EBC, i.e. at start of neoadjuvant treatment for patients receiving neoadjuvant thera-py or at start of adjuvant treatment if no neoadjuvant therapy is given. Treatment can be cytotoxic, endocrine, or targeted substances, what-ever was given first ABC cohort: * Female and male patients with advanced breast cancer (stage IV defined as synchronous or metachronous diagnosis of distant metastases at inclusion) * Patients at the start of their initial first-line systemic treatment for ABC, which can be cytotoxic, endocrine or targeting a specific signaling pathway, whatever is given first All cohorts: * Written informed consent * Patients participating in the PRO module: signing of informed consent form and completion of baseline questionnaire before start of initial systemic treatment for EBC or systemic first-line treatment for ABC * Patients not participating in the PRO module: within six weeks after start of initial systemic treatment for EBC or systemic first-line treatment for ABC * Age ≥ 18 years Exclusion Criteria: * Patients with prior systemic therapy (cytotoxic, endocrine, or targeted) for EBC or ABC * Patients who do not receive any systemic therapy for EBC or ABC