The study aims to establish an Italian registry for the implementation of the use of genomic tests in patients with HR +/HER2- breast cancer at intermediate risk of recurrence after the entry into force of the Ministerial Decree of 18/05/2021. The decree has established the reimbursability of genomic testing for breast cancer patients, thereby influencing clinical decision-making and patient management within Breast Units. In addition, the study aims to evaluate the clinical impact of the use of genomic testing on the type of adjuvant treatment, in terms of change of treatment indication by breast units according to the test result.

The study is a retrospective and prospective, non-interventional, observational registry-based study that will enroll all patients with ER +/HER2-negative, T1-3 breast cancer with negative axillary lymph nodes or up to 3 positive axillary lymph nodes for whom Breast Units require genomic test to support adjuvant therapy decisions, according to current clinical practice. For prospective cohort: genomic tests will be performed on all patients who meet the criteria for access to testing as set out in the Ministerial Decree of 18/05/2021, unless otherwise agreed by the reference Breast Unit, in accordance with the specific diagnostic pathways activated by each site. For retrospective cohort: data for patient referred for genomic testing following Ministerial Decree 18/05/2021 will be collected. The patient's baseline demographic characteristics, tumor clinicopathological features, pre and post-test therapeutic indication (CET vs ET), the test results, the actual adjuvant treatment received and time around data will be recorded in a dedicated registry.

Inclusion Criteria:

1. . Age ≥ 18 years

2. PS ECOG 0-1

3. Histologically confirmed early breast carcinoma with positivity for hormone receptors (ER+ IHC >10%) and HER2 negative (IHC value 0 1+ and/or FISH not-amplified)

4. Primary resective surgery for early breast cancer with adequate assessment of lymph node status (sentinel lymph node biopsy or complete axillary dissection), with one of the following diagnostic stages:

   • T1-3, N0, M0
   • T1-3, pN1mic, M0
   • T1-3, pN1a, M0

5. Indication for adjuvant treatment with endocrine therapy (ET) or chemo endocrine therapy (CET), according to the decision of the reference Breast Unit

6. Meeting the criteria for "intermediate" risk, i.e., no "low" or "high" risk of recurrence, as defined in the ministerial decree of 18/05/21:

   • Low risk defined by at least 5 of the following: G1, T1a-b, KI67 < 15, N neg, ER > 80%
   • High risk, defined by at least 4 of the following: G3, T > 2, Ki67 > 30, N pos, ER < 30%

7. Indication for genomic test (Oncotype DX®, Mammaprint®, PAM50 Prosigna®, Breast Cancer Index®, EndoPredict®) by the Breast Unit

8. Ability to provide written informed consent to participate in the registry study, approved by the local Ethics Committee.

9. The patient underwent genomic testing starting from September 2021

Exclusion Criteria:

1. Low-risk and High-risk patients as defined in the Ministerial Decree of 18/05/21
2. ER negative and/or HER2 positive tumours
3. More than 3 lymph nodes involved at clinical/pathological staging
4. Invasive tumours <2mm evaluated by local pathologists
5. Previous history of breast cancer
6. Synchronous breast cancers
7. Multifocal tumours
8. Metastatic disease
9. Contraindications to adjuvant treatments
10. Performance status (PS ECOG) > 1 and / or other clinical factors that would make the patient a candidate and unsuitable for systemic adjuvant treatment or have received an exclusive indication for precautionary hormone therapy as part of the Breast Unit collegial assessment.
11. Psychiatric diagnosis that may affect the ability to participate in this study

The study is a retrospective and prospective, non-interventional, observational registry-based study that will enroll all patients with ER +/HER2-negative, T1-3 breast cancer with negative axillary lymph nodes or up to 3 positive axillary lymph nodes for whom Breast Units require genomic test to support adjuvant therapy decisions, according to current clinical practice.