The purpose of the project is to set up a national, prospective, longitudinal, multicenter cohort study with associated satellites, a tumor registry platform, to document uniform data on characteristics, molecular diagnostics, treatment and course of disease, to collect patient-reported outcomes and to establish a decentralized biobank for patients with breast cancer in Germany.

OPAL is a national, observational, prospective, longitudinal, multicenter cohort study (tumor registry platform) with the purpose to record information on the antineoplastic treatment of breast cancer in Germany. The registry will follow patients for up to five years. It will identify common therapeutic sequences and changes in the treatment of the disease. At inclusion, data in patient characteristics, comorbidities, tumor characteristics and previous treatments are collected. During the course of observation data on all systemic treatments, radiotherapies, surgeries, and outcome are documented.

Health-related quality of life in patients with breast cancer will be evaluated for up to five years.

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 therapy or at start of adjuvant treatment if no neoadjuvant therapy is given. Treatment can be cytotoxic, endocrine, or targeted substances, whatever was given first

ABC cohort I (prospective):

• Female and male patients with advanced breast cancer (stage IV defined as synchrone or metachrone 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

ABC cohort II (retrospective):

• Confirmed diagnosis of HR-positive, HER2-negative ABC (stage IV defined as synchrone or metachrone diagnosis of distant metastases at inclusion)
• Start of initial first-line systemic treatment for ABC, which can be cytotoxic, endocrine or targeting a specific signaling pathway, whatever is given first, between September 2021 and December 2025
• Inclusion is possible regardless of whether patients are alive or deceased at the time of documentation; for patients alive: written informed consent

Prospective 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
• All 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

All cohorts:

• Age ≥ 18 years

Adult female and male patients with breast cancer starting first systemic treatment for EBC or ABC.