Adjuvant Treatment Recommendation and Oncotype DX® in Early Breast Cancer

Inclusion Criteria: \- Patients screening criteria 1. ≥ 18 years old female patients. 2. Resected primary breast cancer (R0 resection). 3. ER-positive breast cancer (defined as at least 10% ER-positive malignant cells). 4. HER2 negativity by IHC (0 or 1+) or by FISH (negative if ratio is ≤ 2.0). 5. pN0 or pN1a (1-3 positive nodes) by sentinel procedure or axillary dissection. All patients matching the screening criteria should be recorded consecutively in the patient screening and enrollment list. Patients inclusion criteria for baseline data collection 1. Signed informed consent form for participation to the baseline data collection. In addition, the following information must be available from the pathology report: 2. Estimation of the pathologic maximum tumor diameter (in mm). 3. Results of ER positive tumor cells (in %) and of PgR positive tumor cells (in %) of the invasive component. 4. Proliferation rate by Ki-67 staining (MIB-1 antibody) in %. 5. Result of modified Bloom-Richardson-Elston (BRE) Grading (Grade 1, 2 or 3). Patients eligibility criteria for participation to the study Inclusion criteria 1. Signed informed consent form for participation to the study SAKK 26/10. 2. The patient is considered suitable to receive adjuvant chemotherapy (ie no medical contraindications to chemotherapy). 3. Invasive breast cancer tissue is available to prepare 39 sections (35 unstained + 4 H\&E stained slides, thickness of 5 µm). 4. Performance Status: 0 or 1. Exclusion criteria 1. Pregnancy 2. Bilateral invasive breast cancer 3. cT4 and pT4 tumors. 4. Patient with a current psychiatric or medical diagnosis that would interfere with her ability to participate in this study. 5. Known metastatic breast cancer (M1).