The study is planned to observe and document the therapeutic decision-making process, treatment protocols, and clinical outcomes in patients with luminal breast cancer, whether they have undergone EndoPredict® testing or not

PRELUDE is a prospective, multicenter, non-interventional registry designed to describe real-world treatment decision-making, treatment patterns, and long-term clinical outcomes in patients with luminal (ER-positive/HER2-negative) early breast cancer who are eligible for EndoPredict® testing, including patients who do and do not undergo the test.

The registry will be conducted at approximately 10-20 sites across Greece (with the option to add sites outside Greece if needed) and aims to enroll up to 2,000 eligible participants within 3 years. Participants may be enrolled after surgical histopathology results are available and before commencement of adjuvant endocrine treatment, and will be followed prospectively once per year for up to 10 years after surgery.

The study aims to assess 5- and 10-year clinical outcomes and to evaluate these outcomes according to EndoPredict® (EP/EPclin) risk groups or scores among patients who undergo testing, in a real-world setting. The registry will also examine which patient and disease characteristics (e.g., age, menopausal status, nodal status, histopathology, EPclin score) will influence adjuvant treatment decisions, in the context of evolving therapeutic standards and recently introduced adjuvant options.

Inclusion Criteria:

• Age ≥ 18 years old.
• Histological diagnosis of invasive breast cancer.
• T1-T3 tumor size.
• 0-3 positive axillary lymph nodes.
• Documented ER-positive tumor by immunohistochemistry (≥1% or Allred Score: ≥3/8 or H-score: ≥50/ 300)
• Documented HER2-negative tumor by immunohistochemistry and/or in situ hybridization
• Subject with signed and dated informed consent form.

Exclusion Criteria:

• History of another primary malignancy within the last 5 years, except for resected non-melanoma skin cancer.
• Pre-operative chemotherapy administered.
• Subject without signed and dated informed consent form.

All subjects diagnosed with invasive breast cancer, pT1-pT3, with 0 to 3 positive axillary lymph nodes, ER-positive, HER2-negative, that have not received neo-adjuvant chemotherapy and therefore are eligible for EndoPredict® testing.