This study examines the impact of an additional tumour test called the 21 gene Recurrence Score (OncotypeDx®), a commercially available test on a Medical Oncologist's decision to recommend chemotherapy.

After a breast cancer and any lymph glands have been surgically removed, further (adjuvant) treatment is generally given to reduce the risk of cancer recurrence. For patients with estrogen receptor (ER) positive breast cancer, this treatment has traditionally been chemotherapy and hormone therapy. However, it is increasingly recognised that tumours which are ER positive and negative for the human epidermal growth factor receptor 2 (HER2), are relatively resistant to chemotherapy. It is likely that many more people are exposed to the risks for chemotherapy than ever benefit from it. In order to select patients who will get more benefit from chemotherapy and to spare those who get very little benefit from side effects, risk assessment tools are being developed.

The 21 Gene Recurrence Score is a test that examines the tumour genes to estimate the risk of the tumour relapsing and possible chemotherapy benefits. Currently, the 21 Gene Recurrence Score (OncotypeDx®) is used In Ireland for patients with no cancer in their lymph nodes. For these patients it can help in deciding who should get chemotherapy. Patients with low scores can sometimes avoid chemotherapy. In some countries, this test is offered to almost all patients with ER positive breast cancer, irrespective of whether the cancer has spread to lymph nodes or not. However, in Ireland this test is not standardly available for patients who have breast cancer involving lymph nodes.

Inclusion Criteria:

General Inclusion Criteria (All Patients)

1. Age 18 years of age or older
2. ER Positive Tumours (≥1% positive cells or Allred score ≥ 2 (Appendix 1))
3. Human Epidermal Growth Factor Receptor 2 (HER2) negative breast cancer (0-1 by IHC or FISH <2.0)
4. No evidence of metastatic disease on CT, bone scan or other imaging
5. Fit for consideration of chemotherapy as determined by the Investigator
6. Adequate performance status (Eastern Cooperative Oncology Group (ECOG) 0 or 1 (Appendix 2))

Inclusion Criteria - Cohort 1 (Postoperative Patients): N= 75

1. Adequate surgical excision of breast tumour (mastectomy or lumpectomy) and lymph nodes (sentinel lymph biopsy or axillary dissection)
2. Any tumour size (T stage (Appendix 3))
3. Involvement of 1-3 lymph nodes (N1, including micrometastases)

Inclusion Criteria - Cohort 2 (Preoperative Patients): N= 75

1. Candidates for preoperative therapy for early breast cancer
2. T2-T4 tumours
3. Involvement of at least one lymph node, (including micrometastases) on biopsy
4. Adequate tissue from core biopsy for 21 gene RS testing (approximate minimum 5mm)

Exclusion Criteria (All patients):

1. ER negative tumour (Allred score 0-1)
2. HER2 positive tumours as defined by IHC 3+ or FISH ≥ 2.0
3. Node negative disease, including those with Isolated tumour cells only (node negative i+/i-)
4. Known metastatic breast cancer
5. Performance status ≥ 2
6. Patients not considered by their treating physician to be fit to undergo chemotherapy.
7. Men with breast cancer.

The study will examine 2 cohorts of patients;

• 75 patients (cohort 1; "postoperative") who have undergone resection of their primary breast cancer and
• 75 patients (cohort 2; "preoperative") who are referred to a Medical Oncologist for consideration of neoadjuvant (preoperative) treatment.

Both cohorts will have ER positive, lymph node positive breast cancer and both cohorts will undergo testing with the 21 gene RS.